Dive Site: Bajo Alcyone

About Bajo Alcyone

Bajo Alcyone, a submerged seamount near Cocos Island, stands as a world-renowned dive site. Discovered and named by Jacques Cousteau's Calypso expedition in 1987, this pinnacle rises from over 2,000 meters of depth to within 25 meters of the surface, creating an ideal environment for pelagic marine life. Diving at Bajo Alcyone offers an unparalleled experience, primarily centered around incredible encounters with large schools of Scalloped Hammerhead Sharks. These sharks are routinely seen in formations of 100 to 300 individuals, especially during peak season, utilizing the seamount's cleaning stations. Beyond hammerheads, divers frequently spot Galapagos Sharks, Silky Sharks, and various ray species, with the occasional appearance of Whale Sharks or Tiger Sharks. The site's remote location approximately 550 kilometers off Costa Rica's Pacific coast means access is exclusively via liveaboard. While the main draw is the abundance of large pelagics, the underwater topography also supports diverse fish schools and unique behaviors like marble rays resting on sandy patches. Conditions can be challenging, featuring strong currents and depths reaching 30-40 meters, often accompanied by cold thermoclines. This makes Bajo Alcyone best suited for advanced divers with experience in drift diving and deeper profiles.

Dive site facts: Bajo Alcyone

Depth

25–40 m

Typical dive

25–30 m

Current

Strong

Visibility

15–30 m

Water temperature

21–27°C (surface), 19°C (below 25m thermocline)

Entry

Tender / negative entry

Level

Advanced, current experience essential

Dive type

Pelagic, seamount, shark diving

Region / port

Cocos Island, Pacific Ocean

Coordinates

5.49, -87.06

Conditions & Currents

Currents at Bajo Alcyone are consistently strong, requiring advanced diving skills and experience with drift dives. Divers typically position themselves in the current shadow on the upcurrent side of the seamount to observe marine life. The thermocline can also be significant, with water temperatures dropping to 19°C below 25 meters.

Marine life & sighting chances

Scalloped Hammerhead Shark

Year-round, peak June-November · common

Galapagos Shark

common

Silky Shark

occasional

Whitetip Reef Shark

common

Giant Manta Ray

May-December · occasional

Marble Ray

common

Whale Shark

May-December · rare

Tiger Shark

rare

Tuna

common

King Angelfish

common

Barberfish

common

Oceanic Whitetip Shark

occasional

Dive profile & how the dive runs

Diving at Bajo Alcyone typically involves a negative entry to quickly descend to the seamount's top, which begins at about 25 meters. Divers then position themselves in the current shadow on the upcurrent side, often at depths between 25 and 30 meters, to observe the resident hammerhead schools utilizing cleaning stations. The dive progresses along the seamount, exploring its various flanks and sandy patches where marble rays congregate. Due to the deep profiles and strong currents, bottom times are carefully managed, and divers must be proficient in buoyancy control and drift diving. Safety stops are performed in the blue, factoring in potential thermoclines and current variations during ascent. Descents can reach 40 meters, making Nitrox highly recommended for extending bottom time.

Underwater photography

Bajo Alcyone offers phenomenal wide-angle opportunities, primarily for capturing massive schools of Scalloped Hammerhead Sharks. A fisheye or wide-angle rectilinear lens is essential to encompass the large formations. Due to often-present thermoclines and varying visibility, be prepared for shifting light conditions; strobes are critical to bring out colors and add definition to subjects in deeper water. Mastering buoyancy control is paramount, especially when positioning yourself in currents for extended periods. Patience is key, as shark schools may circle for a while before coming into optimal photographic range. Focus on capturing the natural behavior at cleaning stations while maintaining respectful distance.

Combine with nearby dive sites

• Dirty Rock

  A rock formation known for diverse shark species and schooling fish.

• Manuelita

  Features a coral garden, suitable for macro life and shark encounters.

• Dos Amigos

  Big Dos Amigos is one of the premier dive sites located on the southern side of Cocos Island, approximately 342 miles off Costa Rica's…

• Chatham Bay

  Chatham Bay serves as a pivotal and popular dive site at Cocos Island, strategically positioned on the northeast side of the bay, off…

• Lone Stone

  Lone Stone is a small, solitary rock pinnacle emerging from the deep waters surrounding Cocos Island, approximately 550 kilometers off…

Getting there & logistics

Access to Bajo Alcyone and the rest of Cocos Island is exclusively via liveaboard. Trips typically depart from Puntarenas, Costa Rica, following a 36-hour crossing each way. The nearest international airport is San Jose (SJO), from which a 90-minute drive connects to Puntarenas. Liveaboard itineraries usually last 7 to 10 nights, dedicating significant time to diving Cocos Island's various sites. Transfers from San Jose to Puntarenas are often arranged by liveaboard operators. No hotels or independent access are permitted on Cocos Island, as it is a protected national park. Park fees are typically included in liveaboard packages, but confirm this with your operator.

Safety & environment

Diving at Bajo Alcyone is strictly for advanced divers due to strong currents, deep profiles reaching 40 meters, and cold thermoclines. It is imperative to have experience in drift diving and excellent buoyancy control. The nearest recompression chamber is on the Costa Rican mainland, approximately 36 hours away by boat, making medical evacuation a significant challenge. Comprehensive dive insurance, including coverage for remote medical evacuation, is non-negotiable. Always follow your dive guide's instructions precisely, especially regarding current positioning and ascent protocols. Maintaining appropriate gas management and respecting bottom times are critical for safety in this remote and challenging environment.

Who it suits — and who it doesn't

FAQ

Bajo Alcyone FAQ

Liveaboards diving Bajo Alcyone

These liveaboards may visit Bajo Alcyone on selected itineraries — the exact dive sites depend on departure, weather and conditions.

Cocos Aggressor

Costa Rica

22 guests37.8 m

$636/day

Sea Hunter

Costa Rica

20 guests

$690/day

Okeanos Aggressor II

Costa Rica

24 guests36.6 m

$504/day