Cocos Island · Costa Rica · Seamount
Bajo Alcyone
Wedge into a crevice at 25 m and wait for the hammerheads
Photo: Barry Peters` · CC BY 2.0
Bajo Alcyone is a seamount about 1.5 km off Cocos Island whose summit sits at 25 m, deep enough that the dive begins with a fast drop rather than a swim. Divers settle into the rock and wait: scalloped hammerheads glide in until they fill the field of view, and mobula, manta and eagle rays work the same open water. Rough seas and often strong currents keep it to advanced divers.
Where it is and how deep
5.5103° N, 87.0291° WApproximate position — the dashed circle shows where the site lies; your operator's briefing has the mooring.
The dive
The descent is fast and vertical. You go straight from the surface to the seamount top at 25 m before the water pushes you off the rock. The site sits about 1.5 km off the island in open ocean, and the exposure that comes with that shows up on the entry more than at any other stage of the dive.
Once you are down, the dive is a wait rather than a tour. You find a crevice to wedge into on the summit, keep still and watch the blue above the ridge, and the hammerheads gently glide into the picture until they fill your entire field of vision. Mobula, manta and eagle rays pass through the same water off the edge of the rock. When the group leaves the summit the safety stop is done out in open blue rather than on anything solid.
Marine life and season
- Hammerheads
- Mobula rays
- Manta rays
- Eagle rays
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Good | Good | Good | Good | Good | Prime | Prime | Prime | Prime | Prime | Good | Good |
Season follows Cocos Island: June to October brings the hammerhead schools; December to May is the dry season, with calmer seas and clearer water.
Know before you go
- Exposure to rough seas and often strong currents: the entry has to be a fast negative descent, and coming off the rock early means finishing the dive drifting in open water.
Photos from Bajo Alcyone
Kris Mikael Krister · CC BY 3.0
Kris Mikael Krister · CC BY 3.0
Kris Mikael Krister · CC BY 3.0
Dive videos
Cocos Island Diving at Alcyone · Jean-Marc Thimon on YouTube
Alcyone-BFDC_BottomCAM · ncwreckdiving on YouTube
Questions divers ask
How deep is Bajo Alcyone?+
The seamount top sits at 25 m (82 ft) and the dive is a quick descent straight down to it. That depth, combined with often strong currents and rough surface conditions, is why operators ask for advanced certification here.
Sources
- Cocos Island Dive Sites — Dive The World
- Alcyone - ScubaGo — ScubaGo
Photo credits
- Two scalloped hammerhead sharks cruising in open blue water off Cocos Island by Barry Peters`, CC BY 2.0, via Wikimedia Commons
- Scalloped hammerhead shark swimming over the reef in blue water by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
- Close head-on view of a scalloped hammerhead shark's wide-set eyes by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
- Round ribbontail ray gliding close to the camera over rock by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
In The Logbook
- Where to dive in every month of the yearTrip planning · 14 min read
- What is decompression sickness (the bends)?Body & health · 18 min read
- How long to wait before flying after divingBody & health · 8 min read
- Why your ears hurt diving, and how to stop itBody & health · 8 min read
- When and where to dive with hammerheadsBig animals · 16 min read
- Liveaboard vs resort diving: which suits you?Trip planning · 6 min read
More dive sites in Cocos Island
Hammerheads and marble rays swim right up to you at 20-25 m
An arch wide enough for the whole group, with hammerheads coming through
Reef
Whitetips hunt the coral garden by torchlight
Galapagos sharks over a crown with no shallow water anywhere
Similar dives elsewhere
A volcanic seamount that shows at low tide and drops to 35 m
The old thresher shoal, now dived for tigers and mobulas
Current-swept seamount with hammerhead schools in Jan and Feb
.jpeg){kind=link}
.jpeg){kind=link}
.jpeg){kind=link}
Fusiliers roll down the slope thick enough to block the view.