Diving in Cocos Island
Costa Rica Scuba Diving at its Best!
Situated in the Golden Triangle, 550 km off the mainland of Costa Rica, the converging nutrient-rich currents from nearby deep water attract multitudes of pelagic action to Cocos.
The island has around 20 dive sites all in a compact location, from shallow but steep vertical walls, drift diving, to deep pinnacles down to over 40m, and blue water dives. All sites are close to the island and one another, making it an ideal liveaboard diver's playground.
Declared a marine national park by the Costa Rican government in 1978, the Isla del Coco is a large uprising of volcanic seamounts covered with untamed and uninhabited tropical rainforest featured in breathtaking scenes in the movie 'Jurassic Park'. The eco-system has been largely untouched by humans, offering us a rare glimpse into a world where nature reigns supreme, allowing the marine and island creatures to interact undisturbed and thrive in the process.
The main attraction of Cocos Island diving is scalloped hammerhead sharks. You will witness wave after wave of huge groups of hammerheads, some numbering in their hundreds! But there are other regular shark species encounters too, most notably whitetip reef sharks and Galapagos, silky, tiger, blacktip, silvertip and guitar sharks. They are joined by many different species of rays: mobula, marble, manta and eagle rays swirling around you in search of cleaning stations.
Bajo Alcyone is the number one Costa Rica diving spot to see hundreds of hammerhead sharks and large fish action. Descending to the submerged mountain will give you the best seat in the house to see manta and mobula rays swirling into the cleaning stations and legions of hammerhead sharks on all sides of you as they descend to below the thermocline.
Dirty Rock is another spot for intense pelagic action; this site being more suitable to lesser skilled divers as the channel between the boulders and pinnacles forms a sheltered refuge. Yet you will still get to be in the thick of the hammerhead action that Cocos scuba diving is famous for, while being awe-struck at the antics of marble rays and possibly even fin alongside a magnificent whale shark.
Moray eels are very visible as they weave and sway from every available crevice in the sheer volcanic wall. Fissures in the wall are filled with smaller fish hiding from the shoals of jacks, who in turn attract a bevy of whitetip reef sharks.
Dive Site Descriptions
Bajo Alcyone - is unparalleled as the place to see hammerhead sharks. After a quick descent to the seamount top at 25m, find a crevice to wedge into and the hammerheads will gently glide into the picture until they fill your entire field of vision! From viewing their distinct hammerhead silhouettes at the surface to watching them descend below you, you will be spoilt for choice with photo ops.
The hammerhead sharks prefer swimming below the thermocline which often tempts divers to descend below 30m. The depth of the dive, coupled with the exposure to rough seas and often strong currents, makes it advisable for you to be an advanced diver to enjoy the many advantages of this site.
Due to its offshore location about 1½ km from the island, you will find incredible pelagic action at this spot promising you numerous fulfilling interactions with mobula, manta and eagle rays. Shark cleaning stations abound with many satisfied customers among the silky sharks and Galapagos sharks. Majestic whale sharks are also frequent visitors. At Bajo Alcyone you will be spoilt, not only with shark numbers but also variety.
There is also some life on the reef too, if you can tear your attention away from the shark action. The rocks are home to many octopi and they can often be caught in their amorous mating ritual, as if aware that your attention mainly lies elsewhere. The crevices are also home to the rather bizarre mottled soapfish, which lie flank down on the sand as if pretending to be dead.
As you ascend into the blue for your safety stop you are likely to be accompanied by schools of jacks and the occasional yellowfin tuna. Truly this Costa Rican dive site needs to be dived to be believed.
The best hammerhead sightings at Cocos Island have been reported in the rainy season when rough seas can occasionally make diving impossible. However, the weather is changeable with many a sunny day in between the torrential rains, making the site accessible all year round and your perseverence will always be rewarded, in the most spectacular manner.
Dirty Rock - Made up of volcanic boulders and rock pinnacles rising just above the waves and separated by a sheltered 100m channel, this site is the most popular spot for diving at Cocos Island due to the sheer volume of hammerhead sharks and the incredible bio-mass of fish that congregate here.
A swift descent to 20-25m gets you right to where all the action takes place with hammerhead sharks being surrounded by attentive barberfish. All you need to do is watch the magnificent show as it unfolds around you. Hammerheads and marble rays will swim right up to you; around, above and below you. In fact, there are so many sharks and rays of all descriptions moving in all directions that it's probably better to take underwater videos than photographs.
Masses of large reef fish such as leather bass and amarillo snapper sway idly in the surge whilst other smaller snapper species and goatfish harbour in the rock crevices. Large shoals of bigeye jacks, bluefin trevally, hunting tuna and blacktip sharks swerve around the boulders and up into the blue, and the occasional whale shark will majestically cruise into the channel just to make your day.
Gently ascending along the spectacular rock formations brings you into contact with green and hawksbill turtles foraging in the coral. Divers taking safety stops here are often joined by groups of playful bottlenose dolphins. In fact, this is one of the most dynamic Cocos Island dive sites, with probably the best all star line up you could find anywhere in the world!
You can dive Dirty Rock at any time of year. On a Cocos liveaboard cruise you will get the chance to dive this site more than twice and still want to come back for more big fish interactions.
Dos Amigos Grande - This dive site, being the larger of the 'Two Friends', is dominated by a magnificent arch in its southwest corner. Descend to 25m where you can marvel as the arch rises from a depth of 28m to 19m below the ocean's surface. The swim through is so large your whole dive group can fit through comfortably.
Hammerhead fans will not be disappointed by the schooling sharks swimming through the arch together with whitetip reef sharks, eagle rays, and a healthy population of snappers and jacks. Large graceful marbled rays will delight you with their antics as they appear around the curve, almost brushing up against you.
While you allow the current to carry you away from the arch along the small islet's wall, you will be engulfed by yellowtail snappers and rainbow runners. Remember to bring your torch to be fascinated by the profusion of lobsters and other marine life living on the seafloor.
Depending on the current, your dive could either start or end at the arch. If you begin at the arch, your final destination is at the other end of the islet. Hover there as long as you can to be entertained by hordes of hammerhead sharks awaiting their turn with the barberfish at busy shark cleaning stations. Tiger sharks also put in frequent visits to Dos Amigos Grande.
The rock formations, specifically the monumental arch, coupled with the large fish interactions with sharks and rays that are mostly unafraid of divers; make this dive a memorable one for your logbook.
Dos Amigos Pequeña - Dropping into the strong surge on the west side and descending down onto the barren volcanic slopes at this remote spot, you can be forgiven for thinking that this site will not deserve a mention among the elite of the Cocos Island sites. However, think again.
As you swim in an anti-clockwise direction, finning with the to-and-fro of the surge, you'll soon begin to note the star attractions. Most places in the world, Hammerhead sharks are extremely and rightly cautious of humans. However, dive at Cocos and you'll encounter a different side to their behaviour.
Here, the sharks are very curious and cruise ever nearer to the patient diver. If you adopt a neutrally buoyant 'head up' posture and wait, you might well be engulfed by hammerheads from all directions. Some cruising down towards you from the shallows, others from right and left, some from the depths below or straight at you from the blue, yet more gently swimming overhead in their distinctive pattern of motion. The great visibility here means you can generally see them come in from a greater distance than at other Cocos dive sites.
Eventually you'll surely run short of bottom time, so continue to circle around the islet whilst ascending as you go. The sharp rocks, which appear bereft of life apart from a few urchins and starfish, are often hidden by huge congregations of blue-striped snappers and creolefish. Eagle rays seek out frequent king angelfish cleaning stations here and they are a delight to see on the slopes so frequently. Oceanic blacktips also frequent Dos Amigos Pequeña, but appear slightly spooked by the more numerous and larger hammerheads.
At the end of the dive, it's best to swim out into mid ocean and away from the islet for your safety stop. This is to avoid the worst of the heavy surge in the shallows. But don't switch off just yet as you can still see some rare oceanic creatures here, such as the heavy set Pacific dog snapper, or wahoo and steel pompano feeding at the surface.
The smaller of the 'Two Friends', Dos Amigos Pequeña is the more southerly of these 2 dive sites. The small conical shaped islet has the best and most consistent visibility that you're likely to encounter when diving in Cocos.
Everest - An undoubted highlight of your Costa Rica trip, or indeed of your entire diving career, could be a truly unforgettable deep dive in a submersible craft. If there is availability and you have chosen to treat yourself then prepare for an unforgettable experience viewing the marine world through a large bubble at depths beyond which you have ever dived.
At Everest you will go close to 90 metres down in the submersible. Look up to see mobula rays swoop overhead or big schools of hammerheads pass by silhouetted against the light colour of the surface. Check out bizarre deep sea creatures like the red-lipped Cocos batfish and slowly ascend up the volcanic mountain experiencing the underwater realm as never before. A dive in Costa Rica with a real difference!
Manuelita Deep - Manuelita Island is a 150m long islet, lying to the north of Chatham Bay, off the northeast corner of Cocos Island. The deeper west side is one of the prime spots to dive with hammerhead sharks.
Rolling off the side of your dive tender, you'll descend from the surface and follow the boulder formations down into deeper water. Pay attention in the shallows as the surge can be quite strong and also because the ledges all the way down are occupied by whitetip reef sharks, marbled rays and Pacific lobster. As you make your way to depth, you'll pass some of the schooling reef fish that are commonly seen when diving at Cocos Island, such as mullet snapper, whipper snapper and burrito grunts.
If you head in a southerly direction, you'll follow the deepest boulders at about 30-35m past cleaning stations with their attendant king angelfish and barberfish. It's these hygienic fish that are so popular with the scalloped hammerhead sharks. These mighty brutes, some about 4m long, circle the sandy bottom waiting their turn to cruise in for a session with the cleaners. If the visibility is good, you can see dozens of hammerheads in the area. Since 2007, tiger sharks have also frequented this dive site, and these fearsome creatures easily outsize the hammerheads.
As an alternative, you might dive along the deeper northern section of the site. Here the terrain is a steep and vertical wall down to 50m instead of boulders, and more schooling fish occupy the area, such as razor surgeonfish, rainbow runners and Pacific creolefish, as well as solitary fish species such as the orangesided triggerfish and guineafowl pufferfish. White tip reef sharks seem to be everywhere here and you'll see more of them than you care to count. Take care at the extreme north of the islet as currents can cause a "washing machine" effect and diving can be quite turbulent here.
The chances are good that you'll dive this site more than once on your Cocos liveaboard. Given the spectacular big shark action that you're likely to encounter, it's unlikely that you'll be complaining too much.
Manuelita Garden - Manuelita Island is a submerged mountain forming an islet to the north of Cocos Island, just out of Chatham Bay. The coral garden, otherwise known as Manuelita Inside, is located on the protected east side of the island and is likely to be the first site welcoming you to Cocos.
This is one of the few coral reef dives in Cocos and the simple formations are home to a myriad of colourful critters. Descending to the outer edge of the coral garden at 22m, you will be met by bigscale soldierfish and spiny lobsters that seem to wave hello as they peer cautiously from the safety of crevices. Parrotfish and blue-striped snappers dart around you, while below yellow Mexican goatfish stir the sandy slope with 2 barbles under their chin, looking for hidden crustaceans to eat. This is definitely not the diving trip to forget your camera at home!
Look out into the blue frequently and you will be treated to hammerhead sharks and numerous marble rays following the nutrient-rich current from the channel on the west side of the island. Tiger sharks are regular visitors to this particular dive site and it is thought that there are over half a dozen that patrol the reefs of Cocos Island.
Back in shallower depths, large trumpetfish and small groups of bluefin trevally hunt in the crevices for juveniles and yellowtail damselfish, distinguished by their yellow tails and bright yellow lips against a dark brown/black body. Schools of razor surgeonfish and Pacific creolefish race over the reef garden in search of food.
Liveaboards from Costa Rica anchor in either Chatham or Wafer Bay at night, so it is serendipitous that Manuelita Inside offers you an exceptional night dive that can more than parallel the exquisite sunsets you will experience above the water. Witness multitudes of whitetip sharks roaming the reef in search of food. Turning on your torch to bring the colours to life will instantly place you in the midst of a frenetic feeding frenzy as the whitetips use your light to hone in on their prey.
By day and night this site will definitely be a highlight of your diving trip to Cocos Island.
Punta Maria - is an underwater mountain lying 500m off the southwest coast of Cocos Island. It is a made up of a large crown at 25m surrounded by deeper sloping walls, and a couple of pinnacles rising to 20m to the north.
Currents can rush over this site so it's best to begin your dive by descending down the mooring line to 30m and then following the surrounding wall with either the crown on your left or right shoulder depending upon the current.
This part of the dive site is a hot spot for the Galapagos shark. These sharks grow to 3½m and can be found in small groups or alone, feeding on fish, squid and octopi. They are often mistaken for silky sharks which are also seen at Cocos. The most obvious distinction between the two is that the Galapagos shark has a first dorsal fin that begins on the back above the inner margin of the pectoral fin, whereas the silky shark's first dorsal fin is positioned further back and beginning behind the rear tip of the pectoral fin.
As you move along the wall to the north of the crown, you'll move past large schools of blue-striped snapper, burrito grunts and Cortez rainbow wrasse, aggregating amongst the rocky formations. As you close in on the northern area, keep your eye out for the telltale signs of cleaner stations manned by barberfish. Stay low and out of sight and you may be rewarded by close up encounters with hammerhead sharks which pull in for a spruce. The hammerheads that attend Cocos Island seem to be more tolerant of divers than in other parts of the world, and a patient diver can get up really close to these wonderful creatures.
Moving on from this deep section, you'll head north again and find the rising pinnacles. Here you can pass the remainder of your dive, marvelling at the schools of jacks that buzz the pinnacles and the wreathing masses of whitetip reef sharks that hunt here. Manta rays sometimes pull in here too as these mighty yet graceful pelagics are partial to regular cleaning sessions as well.
Punta Maria can be a spectacular dive depending on how lucky you happen to be with nature, but it is always a deep dive since their is no section shallower than 18-20m in depth. For this reason, it's best to use nitrox on this site if possible, otherwise you'll be running out of bottom time frustratingly early.
How to Dive Cocos
The only way to get to the island is aboard one of the professional Costa Rica liveaboards that operate in the area from the Pacific town of Puntarenas.
Depending on conditions at sea, the boat trip from the Costa Rican mainland usually takes about 36 hours cruise time. So you will have more than enough time to get to know your fellow divers and prepare your equipment as well as catch up on any R&R you may need before the serious business of enjoying your diving at Cocos begins. This makes for a unique situation where the tourists are almost exclusively divers.
The island is situated near the Equator where 2 weather patterns converge, which results in changeable weather, relatively cool equatorial air temperatures averaging 25.5°C, and average annual precipitation of over 7m.
If you prefer calmer seas and higher visibility then book your trip between December and May - the dry season. Dry season typically sees calmer seas and visibility of over 30m. Rainfall alternates with sunny skies all year round. This however, does not affect the diving action.
In fact, for many, the best time to dive at Cocos Island is in the 'rainy' season from June to December, when the nutrient upswells attract multitudes of hammerhead sharks, as well as manta rays and whale sharks. The surface is rougher during this period and visibility drops to within the range of 10 to 25m. Plankton rather than rainfall is more likely to be the factor that reduces visibility. The long open ocean crossing is likely to be less comfortable during rainy season.
Water temperatures hover between 24-30°C (average 27.8°C) and there is a seasonal variation of only a degree or two. However, temperatures can vary dramatically, dropping up to 6°C due to thermoclines. This can be an arresting sensation if you are inadequately suited. We recommend a 5 mm full length wet suit, hood, gloves and boots to be prepared for all eventualities.
So it is all a matter of preference when is the 'best' time of year for a visit to scuba dive this Costa Rican island. August and September are the 2 most popular months. June and July are said to hold the promise of both calm seas and a good chance to see the big creatures.
Good for: Large animals, hammerheads, and advanced divers
Not so good for: Wreck dives, beginners, non-diving activities, and small animals
Depth: 10 - >40m
Visibility: 12 - 30m
Currents: Moderate to very strong
Surface conditions: Can be rough and choppy further from shore
Water temperature: 24 - 30°C
Experience level: Advanced, mandatory surface marker buoy
Number of dive sites: ~20
Distance: 550 km west of Costa Rica
Access: Cocos liveaboards
Recommended length of stay: 10 days