I spent 10 days diving Cocos island on the Okeanos Aggressor 2, and this is my review of the boat and the trip. Read on to find out if it is the boat for you and for practical tips. Cocos is known as one of the best dive destinations in the world. Find out if the reputation is justified.

Read the Okeanos Cocos Aggressor review and see how it went!

Arriving on the Cocos Okeanos Aggressor

The Aggressor departs from Puntarenas, a small town 90 minutes from San Jose, the capital of Costa Rica. You are asked to spend the night before in San Jose to meet their shuttle bus early in the morning. It does make sense because if you miss the boat departure for any reason, there is no way to catch up with it the next day as the boat starts by navigating for 36 hours.

As I was already in Costa Rica doing a Marine conservation expedition, I went directly to Puntarenas and spent two nights there. It was a let-down. The town is not the most exciting place in Costa Rica. The houses are heavily protected with metal barriers and barbed wires, giving them a scary look. I didn’t feel comfortable walking alone in the streets and have been told the place could be dangerous.

Tip: I recommend spending the night in San Jose rather than in Puntarenas and meeting the Aggressor shuttle bus transfer as suggested by Aggressor.

Review of the itinerary around Cocos Island  during the Okeanos Aggressor liveaboard

Day one and two: Navigating to Cocos island

Cocos island is a whopping 36 hours of navigation from the mainland. The distance from any land or humans and the protection of the area make it an exceptional place to dive!

We boarded around 2 pm, were shown to our cabins, and attended the safety briefing.

We were lucky to have very calm water, making the crossing pleasant. It was a lazy day and an excellent way for all the people flying from abroad to refresh, adjust to jetlag and meet the other passengers.

We saw a massive pod of dolphins hunting, and the sunset was spectacular.

Day three: first encounter with the hammerheads

We arrived at Cocos Island’s Chatham Bay around 4 am, and it was raining hard.

After breakfast, we went for our first dive at Manuelita coral garden dive site outside the Manuelita island. It is a shallow sloping reef, starting around 6 meters and sloping down to a sandy bottom at 18 meters. It is an easy dive and perfect for a check dive.

We saw a few blacktip sharks as we went down.

Within five minutes, we saw a school of six hammerheads. They hung out with us for about 10 minutes. It was awesome!

We continued the dive and saw an octopus, a turtle, and a marble ray. The place is also full of small fishes and is covered by small coral patches. Best check dive ever!

And the water was warm at 29 degrees. So whoever tells you that you have to go to 40 meters and have cold water to see hammerheads is lying 🙂

We did two more dives around Manuelita Island. The Manuelita channel dive site is between Manuelita Island and Cocos Island. It goes down to about 30 meters. There is a cleaning station on the west side, which is a great place to spot sharks. Again, we saw plenty of hammerheads, with some of them coming really close to us.

The last dive was the Manuelitas outside dive site, the exposed western side of the island. It can face strong currents and is usually a drift dive. There are three cleaning stations along the wall, and it ends up in a sandy bottom.

Over the course of the day, I think we saw over 70 hammerheads!

We also saw five golden cow rays cruising by and a few marble rays.

The most astonishing was a massive school of Jacks mating. They were dancing two by two. The larger of the two fishes turned black while the other remained white. There were tens of couples dancing together. Amazing!

After the dives, we went for a small hike on top of Chatham Bay.

A path is going up, so the walk is not challenging but slippery. The soil at Coco’s is extra greasy after rain due to its clay content.

Tip: Bring walking shoes. Mosquito repellent is not necessary as there are no mosquitos on the island.

The view from the top was beautiful. We saw many birds and a few feral pigs.

On the beach are many rock carvings from the early explorers. The oldest one dates from the 18th century, and there is even one done by Jacques Cousteau!

Day 4: Strong current and more hammerheads at dirty rock dive site.

Today, we got the authorization to do four dives. The boat moved to Wafer Bay at 5:45 am.

The first dive was at the Viking Rock dive site. It is a small island situated at the entrance of Wafer Bay with a steep wall. As we dove at 6:45 am, the site was still in the shade, and it wasn’t fantastic.

The second dive at Manuelitas dive site saw plenty of hammerhead action and was fantastic.

The third dive at Dirty Rock had to be aborted due to the strong current, but we would get more chances to dive Dirty Rock later in the week. The fourth dive was over a small coral reef at the Pan de Azucar dive site. This is a site where you can find frogfishes, but there was too much current today for our group to find it.

I busted my ear and had to skip the last three dives of the day. This is most divers’ worst nightmare to be unable to dive after traveling so far and being on a liveaboard. But I made the best of my time on the boat for the rest of the day by relaxing on the top deck and enjoying the view over Chatham Bay. There is always something going on when you are out at sea. You might sometimes see birds circling an area in the distance and plunging into the sea. As you get closer, you might see fishes jumping out of the water and sometimes even dolphins.

After the dives, we went on a scenic boat ride to see the sunset over Dirty Rock, took a closer look at the waterfalls, and even entered a small cave with the boat.

Day 5: Tiger shark action

The boat moved back to Wafer Bay in the morning. Today, we dove Alcyone, Cocos Island’s most famous dive site.

It is a group of rocks that starts about 25 meters depth and goes down to 50 meters. It is one of Cocos’ deepest sites, and it is out in the blue, attracting many large pelagics.

The current at the surface was powerful, but they have installed a line to go down, making it more manageable.

Tip: Bring gloves as the barnacles on the line are sharp. I don’t dive with gloves and had a few cuts after coming down the line.

As I came down, a Tiger shark was cruising by. He was huge! Fortunately, he didn’t come too close, and he left us before I had time to stress about it.

The line comes near the cleaning station, which is also the best spot to see sharks, which is very convenient.

The schools of fish were impressive. Fusiliers, yellow snappers, and Jacks were there en masse. Giant tuna and many hammerhead sharks made an appearance.

Whitetip sharks were also patrolling the area, but by now, we almost don’t see them anymore… this is how spoilt we have been so far with the diving and the sharks. Alcyone is considered one of the best dive sites on the planet to see hammerheads, and it is easy to see why. They are everywhere!

On the way up, we also saw a few salps floating in the water

After the third dive, the captain took the boat for a sunset cruise around Cocos Island. The landscape is stunning, and the sunset was mesmerizing. All the guests mingled and enjoyed beers on the top deck. The sound of the waves and the thousands of birds hunting before sunset made it a special moment.

Day 6: More hammerhead actions

Today is the full moon. The day’s first dive was back at the Manuelita outside dive site for more hammerhead action. They were there in large numbers again.

We then tried our luck again at the Alcyone dive site. After yesterday’s Tiger shark and hammerheads, we were curious to see what it could bring. It is definitely one of the best dive sites in the world!

A school of thousands of Jacks closed down on us as we came down. The sea became black! In the background, 20 or 30 hammerheads were cruising by. Add the fusiliers and yellow snappers schools, and you have an absolutely magical dive!

We did the safety stop drifting in the blue and were visited by another small school of hammerheads.

In the afternoon, we visited the ranger station in Wafer Bay. We walked over the Rio Genio bridge that has been made entirely from material confiscated from illegal fishing.

Some people chose to swim in the river Rio Genio. Three people from our boat went on a full-day hike to Cerro Iglesias. It was a strenuous hike that took them 11 hours, but the pictures they came back with were beautiful. The cloud forest looked very impressive, with trees covered by moss.

They were accompanied by a park ranger from Cocos Island.

Day 7: More hammerheads

I had to stay on the boat as my ear had gotten worse, but I could still enjoy some action without getting wet.

A considerable hunt was happening around the boat with dolphins, Blue trevally, and sharks hunting fishes. The boobies and frigate birds soon joined it and were fantastic to watch.

There are 149 species of birds in Cocos, so it is an excellent place for bird lovers.

The group did their first dive at the small dos amigos dive site.

Two small islands near each other form this dive site with a channel between the two islands. It is deep as the wall goes down to 45 meters. Big pelagics often visit the cleaning station, and it is an excellent place to find the Galapagos sharks.

They tried their luck again at the Dirty Rock island dive site. It is a wall surrounding the island, and there is another submerged pinnacle to the west at around 30 meters. Many hammerheads cruise by. The wall is made of dramatic stones, some of which have pretty coral.

We then went for a hike to the waterfall. You have to walk through a small river for about 20 minutes. It is very slippery but worth the effort as you can swim at the bottom of the waterfall while enjoying the view.

For dinner, the chef made a beautiful display with sushi! They tasted as good as they looked.

Day 8: Shark galore and dolphins!

Today was a rainy day, but it didn’t prevent us from having amazing dives!

Our day started well at the Manuelitas deep dive site. The site was teeming with hammerheads. They were absolutely everywhere and appeared through the whole dive. Some in small groups, some in groups of 20. Two of them came very close to me, so close I could see their teeth! What a look they gave me! Blacktip sharks were also everywhere. I now understand what it means to swim in a shark-infested sea! We also got to swim with a huge school of Jacks.

The second dive was at the Punta Maria dive site, the western tip of Cocos Island.

It is a submerged rock that starts at around 20 meters. There is a canyon and then another long pinnacle. You go down with a line. The current was mild, but the site was teeming with life. The usual hammerheads were around, but we found many different sharks here. A silvertip shark was inquisitive and kept circling around and getting close to us.

A Galapagos shark cruised by. We could hear dolphins underwater, but we could not see them. As we were coming up, it became the best safety stop ever. A small school of hammerhead sharks cruised by.

I heard the dolphins’ voices getting stronger, and I could finally see a group of six approaching, swimming slowly towards their destinations. I captured a few pictures, and then the dolphins turned back and started to check us out. I had the diving moment of a lifetime as dolphins began to inspect me and dance around us. Then the dolphins decided to come and play with us. They seemed genuinely excited to see us and danced with us for over 10 minutes. A silky shark, followed by a school of fishes, decided it would be an excellent time to make an appearance. What a dive! We were exhilarated and couldn’t stop smiling all the way back to the boat. The dolphins seemed sad to see us go. They wanted to play some more, came to the surface, and made acrobatic jumps just for us!

The third dive was at Dirty Rock dive sites. It also didn’t disappoint. There was minimal current, so we could go around the whole island. We saw three eagle rays floating majestically. Plenty of hammerheads and the biggest school of Jacks ever. Thousands of them turned the sea black. We finished the dive in the blue and were at one point surrounded by over 30 hammerheads.

The fourth dive was at Chatham Bay and was memorable for the large mobula cruising by towards the end of the dive.

What a diving day this had been! It almost didn’t matter that it had been raining most of the day and that the visibility wasn’t great.

The evening program was a beach barbecue, but the torrential rain forced us to have it indoors. The meat had been grilled on the top deck, so it still felt like a barbecue.

Day 8: Last day of diving. Big waves and more rain.

It was still raining when we woke up, but it didn’t prevent us from having a great last day of diving.

The first dive was at the Small Dos Amigos dive site. Dos Amigos are two small round islands on the western side of Cocos.

It was a 30-minute adrenaline-filled ride on the panga to navigate through the large waves.

Small Dos Amigos is the most exposed island, while Big Dos Amigos is closer to the main island. Big Dos Amigos is famous for its underwater arch made of stones. Small Dos Amigos has more wildlife.

The current was strong and the visibility bad. But it was worthwhile as 10 -15 Galapagos sharks were swimming at about 30 meters depth.

To illustrate how good Cocos is to see hammerheads, this was the only dive in Cocos where we didn’t see a hammerhead shark!

Our second dive was back at the Dirty Rock dive site. We were initially going to dive Big Dos Amigos, but the large waves and distance from the boat made us reconsider, and choosing a dive site nearer  Dirty Rock once again didn’t disappoint. While the visibility wasn’t great, it was full of hammerheads.

The last dive of the trip was back at the Manuelita deep dive site. The current was also powerful, and the hammerheads were there en masse.

We said our goodbyes to Cocos around 4 pm as we started our 30-hour journey back to Puntarenas.

Day 9: Cruising back to the mainland

Today was a lazy day as we would be on the boat the whole day. Fortunately, the rain had stopped, and we could enjoy the top deck in the sun.

The crew had been doing a movie during the whole trip, and they premiered it in the afternoon.

It was followed by a small party to honor the “iron divers.” Aggressor liveaboards have this tradition that everyone who does all the dives during the trip gets a medal.

Day 10: Early arrival to Puntarenas and transfer to San Jose.

We arrived in Puntarenas around 4 am and were ready to disembark about 8 am after the last breakfast on board. The Aggressor bus took us back to the airport (or the hotel for people staying a few more days in Costa Rica). I had a 1 pm flight and was too early for the check-in, so I went to wait in the upstairs restaurant in the arrival hall.

Tip: If you need to do an antigen test for your flight, there is a testing center near the airport where the bus can drop you off.

The passengers on the Okeanos Aggressor

There were 18 passengers. Ages ranged from 24 years old to 73 years old!. Most passengers were from Europe and North America.

Most passengers also tended to be well-traveled and good divers with a minimum of about 100 dives. The atmosphere on the boat was incredibly friendly.

Review of the diving organization on the Okeanos aggressor

Cocos National park and Aggressors diving rules

As Cocos Island is a marine conservation area and national park, specific rules must be observed while diving here.

The most important one for divers is that night dives are not allowed anymore. So boats usually offer three dives a day, which might seem little for hardcore divers who have been on other liveaboards that dive four or five times a day. Dive time is 8 am, 11 am, and 3 pm.

The Okeanos was good in offering two extra early morning dives, so we got two days with four dives a day.

The Cocos marine park fee is 560 USD, and this has to be paid on board. It is one of the highest marine park fees I have seen. But you pay for exclusivity as only 60 divers are allowed in Cocos Island at any time, so it never feels crowded.

Tip: Having a dive computer is mandatory, so make sure you bring one.

The maximum depth is 35 meters, and the maximum bottom time is 55 minutes. It was usually enough as the dives are deep, and we would usually run out of air or bottom time by then.

Solo diving is not allowed, and neither is decompression diving.

Blue water diving is not recommended as the currents can be dangerous, but we would sometimes do the safety stop in the blue.

For safety, the Aggressor Okeanos provides nautilus GPS trackers to every diver. Should you drift into the ocean, they will be able to find you.

In case that’s your hobby, be aware that treasure hunting is prohibited on Cocos Island 🙂

Pangas diving

All the dives are from pangas (tender boats). We were separated into two groups of nine divers each.

The crew took care of the tanks and equipment, so we only needed to bring our mask in the panga.

The panga is well-designed and comfortable. It has a good ladder to get on and off the panga and makes diving easy. Most divers would come up with their tank on their back, but the crew could also assist you if you had difficulties with that.

Most dives are done with negative entry backrolls, so make sure you master that before your trip to Cocos.

Tip: The current would often be strong and require intense finning. Bring some diving socks to avoid blisters.

Review of the dive deck on the Okeanos Aggressor

The dive deck is spacious and well-organized. With 18 divers, it felt spacious. You will be assigned a space at the beginning of the cruise with a storage box underneath a seat.

Towel service is organized. Diving towels have your cabin number on them and would be dried off for us so we would have a plush and warm towel waiting for us after every dive.

Fruits or cake are offered after every dive. After the last dive, they even provided hot chocolate that you could spice up with coffee liquor!

Dive briefing and diving groups

The dive briefings were informative. They have well-drawled maps of each dive site.

We were split into two groups of nine divers, which might sound large. But they were clever to have the two groups diving to different dive sites simultaneously so that it never felt crowded underwater.

Aggressor liveaboards are famous for allowing divers to dive independently in buddy teams. In most dives in Cocos, all the divers choose to stay with the group. Maybe the strong currents or the considerable number of sharks made people feel more comfortable in groups. Most divers in my group were quite advanced, so they spread out, and the group size didn’t feel too big.

Water temperature when diving in Cocos island

I was there in April, the end of the dry season. The water temperature was 28 or 29 degrees. We encountered a few thermoclines, and the water temperature would go down to 21 degrees for a short time.

Tip: Bring a 3mm or 5 mm wetsuit.

When to dive Cocos Island?

Cocos Island has a wet and a dry season as you can see on the chart below.

We did the trip in April which is the beginning of the rainy season and we experienced a lot of rain during the trip.

There is no bad time to dive Cocos Island as the fishes and hammerheads seem to be always there. However, the rain and stormy weather would often reduce visibility underwater.

Is diving the Cocos Island good for beginners or snorkelers?

There are so many sharks everywhere that I would not recommend snorkeling in Cocos island.

The current can be strong, and most of the dives are negative entry, so I would recommend it for experienced divers only.

it is however one of the most rewarding dive destinations for sharks and large schools of fish so it is definitely worth the extra efforts

Furthermore, controlling your buoyancy and staying calm underwater is critical when encountering potentially dangerous sharks.

Do you need Nitrox on a diving trip to Cocos?

Most dives in Cocos are between 20 and 35 meters, so using NitroxNitrox will give you significantly more bottom time. I, therefore, recommend it on this trip. It is available for 150 USD for the trip. If you are not Nitrox certified, they offer the course onboard for a fee, and you can do it on the first day.

Review of the Okeanos 2 liveaboard.

The Okeanos 2 will not win any beauty prizes, but it is an extremely well_built boat. In order to dive Cocos Island, it needs to travel 500 kilometers and be able to withstand rough seas. It is a tough and compact boat. I think it might be one of the liveaboards that navigates the longest for a diving cruise on a regular basis. It is easy to navigate with easy stairs and lots of handles. You can see that the boat is well-designed.

We were 18 passengers during the cruise, and the boat never felt crowded.

Main Deck

The main deck has an open-air dive deck at the back. The dive deck is spacious and well-organized. They have a whiteboard there to do the dive briefing and a tank to rinse cameras.

The tenders are right nearby and are easy to board from both sides of the boat.

The restaurant is also located on the main deck. It is a large airconditioned room with four tables, a bar area, and a lounging area with a few sofas. The large panoramic windows overlooking the sea make it a pleasant room, and it was never crowded.

Top Deck

The top deck has an outdoor area with three tables and a few lounge beds to relax. This area is covered and protected from the sun and was my favorite area on the boat to relax in between dives. A fridge with beverages is on this deck, so you don’t need to go down to the main deck to get the sunset beers.

Most passengers would congregate here for sunset drinks, and it was very convivial.

On the top deck are two suites cabins, the captain’s steering room, and a front terrace with more chairs and lounge chairs that were also very pleasant when the sun was coming down.

The below deck has eight deluxe cabins.

We were 18 passengers during the cruise, and the boat never felt crowded. It is easy to navigate with easy stairs and lots of handles. You can see that the boat is well-designed.

Review of the cabins on the Okeanos 2 liveaboard

The bedroom

The cabins are not the strong point of the Okeanos 2 Cocos Aggressor. I stayed in a deluxe cabin (which is the lowest level on the Okeanos 2). The cabins are small with a bunk bed. That being said, they felt bigger in real life than in the pictures. They were also more comfortable than I expected.

The beds are comfortable, and there is plenty of storage room with a large double cupboard and more storage under and above the sink.  There is a TV in the room, and you can download movies to watch from the dining room computer.

Tip: The room air-conditioning is not individually adjustable. Our room was too cold for my taste, so I used my extra sleeping bag. Bring an extra blanket or sleeping bag if you get cold quickly.

Two bathrobes are provided to wear in between dives.

Review of the bathroom

Each room has its own ensuite bathroom. The bathroom is tiny but functional. It has a toilet, and a shower joined together, and it does the job. The water pressure was good, and there was hot water at all times. Boat bathrooms sometimes have a smell, but it was not the case on the Okeanos. The smell below deck was pleasant.

Tip: If you want more space or don’t like bunk beds, book one of the three suites on the boat. They are much better than the cabins below deck, but they get booked up quickly, so make sure you book early.

Review of Crew on the Cocos Okeanos Aggressor.

The crew on board the Okeanos Aggressor is fantastic. Only nine people work for a boat that can host 22 guests, but don’t let that fool you. The service is top-notch.

The captain, Carlos, also acts as a divemaster and is a remarkable person. He is always smiling and is full of positive energy. His good spirits reflect on the rest of the team. It is hard to find a harder working team that always has a smile on their faces.

The dive guides, Carlos and Faicundo, are attentive and know the dive sites well.

The panga drivers are conscientious. I had to abort a dive and came back on the panga earlier. The driver followed the diver’s bubbles during the whole dive and was ready to intervene in an emergency at any time.

Service onboard is also excellent. The waiter is proactive and efficient. The boat is kept incredibly clean, and the drink fridges are always full 🙂 The cook prepared delicious meals.

Aggressor liveaboards are well-known for their outstanding service, and the Okeanos 2 team even exceeded expectations.

Review of the food on the Okeanos Aggressor 2.

Aggressor liveaboards pay special attention to their food, and the Okeanos 2 didn’t disappoint. The food was plentiful, varied, and delicious.

Breakfast is served at  8 am. It is a buffet with cereals, toast, cheese, spreads, bacon, fruits, and yogurt. Eggs are also available on demand.

Lunch would be served at 12:30 and was buffet-style. Each day would have a theme. From Italian to Costa Rican or even sandwich day.

Healthy food lovers will appreciate the huge salad and vegetable selection on offer every day. Dessert was also available.

Dinner was a touch more formal with a tablecloth and a four-course menu. It started with a soup. Appetizers ranged from Caprese salad, heart of palm salads, or Ceviche. The main course ranged from roast beef to sweet and sour salmon with asparagus or chicken breast.

The quality of the ingredients was high, and the cook was great.

Food allergies and preferences were also accommodated. One person in the group was gluten-free, and they prepared special food for her every day.

Special mention for the sushi night. The sushi and sashimi were beautifully presented and delicious.

The island barbeque night was also memorable, but unfortunately, it was pouring rain that evening!

As with all Aggressor boats, all soft drinks, juices, beer, and wine are complimentary.

Tea, coffee, and snacks are also available at all times.

I always bring snacks when I travel on liveaboards but ended up not eating anything I had brought. The food was great, and I did put on weight during the 10 days!

Internet connection during a diving trip to Cocos island

There is no internet on board the Okeanos Aggressor, but it is possible to get a weak connection with your phone.

There is a small antenna near the ranger stations on Cocos Island, so you will get a weak signal while the boat is moored at Wafer Bay during your cruise.

The antenna is from Costa Rican provider Kolbi Ice. My roaming plan didn’t allow me to use it, so I had to buy a Kolbi Ice sim card while on the mainland.

TIP: kolbi Ice is the only network provider that will work in Cocos Island

The signal is very weak. It is suitable for phone calls and SMS. I was able to receive and send WhatsApp messages with patience. And with even more patience, I was able to receive my emails on Gmail. (count about 30 minutes for a message without attachment)

Tip: The connection works best if you are outdoors and high on the boat. It wouldn’t work at all in the cabins.

Concluding my review of the Okeanos Aggressor liveaboard to Cocos Island

Cocos is an extraordinary place for diving. It is probably the best place in the world to see hammerheads consistently. The schools of fish and the number of other sharks are also impressive. Don’t go there if you are looking for pretty corals or nudibranchs! It is a hard place to get to, so few people get to visit, but it is really worth the effort. The Aggressor Okeanos 2 is a great boat with an awesome team that will make you want to come back to Cocos. I had a great time and highly recommend that trip.

Make sure you book well in advance as trips to Cocos island are limited and often fully booked. You can book on the Aggressor’s website

For more information about Aggressors liveaboard, read my review of the Aggressor South Egypt and Belize.

If you want to dive with hammerheads, another great place is the Banda islands in Indonesia in October and November. You can read more about my trips with Ilike, Neomi cruises, and Sea Safari 6 liveaboard.