Cocos Island · Costa Rica · Pinnacle
Dirty Rock
Hammerheads and marble rays swim right up to you at 20-25 m
Photo: Kris Mikael Krister · CC BY 3.0
Dirty Rock is a cluster of volcanic boulders and rock pinnacles breaking the surface off Cocos Island, with a sheltered channel about 100 m wide running between the two main formations. Divers work the rock at 20-25 m, where hammerheads trailed by attentive barberfish and marble rays pass close by from every direction.
Also known as Roca Sucia.
Where it is and how deep
5.5481° N, 87.0819° WApproximate position — the dashed circle shows where the site lies; your operator's briefing has the mooring.
The dive
A swift descent to 20-25 m gets you right to where the action takes place, so there is no drawn-out approach along the rock. The site is made up of volcanic boulders and rock pinnacles that rise just above the waves, and the two main formations are separated by a sheltered channel about 100 m across.
What the dive turns on is what comes past the boulders. Hammerheads and marble rays swim right up to you, around, above and below, and the hammerheads arrive surrounded by attentive barberfish working them over. Bottlenose dolphins have a habit of turning up around the group on the safety stop. It is the most popular spot for diving at Cocos Island, which is as much about how reliably the rock produces as about the rock itself.
Marine life and season
- Hammerheads
- Stingrays
- Dolphins
| 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.
Photos from Dirty Rock
Kris Mikael Krister · CC BY 3.0
Kris Mikael Krister · CC BY 3.0
Kris Mikael Krister · CC BY 3.0
Dive videos
Dirty Rock: Hammerhead Cleaning Station · sulyokpisti on YouTube
Dive at Dirty Rock | National Geographic · National Geographic on YouTube
Questions divers ask
How deep do you dive at Dirty Rock?+
The working depth is 20-25 m (65-80 ft), reached with a swift descent from the tender straight into the zone where the sharks pass. The two main rock formations are separated by a sheltered channel about 100 m across.
Sources
- Cocos Island Dive Sites — Dive The World
- Dirty Rock, Isla del Coco — OpenStreetMap
Photo credits
- Close head-on view of a scalloped hammerhead shark's wide-set eyes by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
- Black and white silhouette of a scalloped hammerhead shark against the sun by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
- Scalloped hammerhead shark swimming over the reef in blue water by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
- Round ribbontail ray gliding close to the camera over rock by Kris Mikael Krister, CC BY 3.0, via Wikimedia Commons
In The Logbook
- When and where to dive with hammerheadsBig animals · 16 min read
More dive sites in Cocos Island
Wedge into a crevice at 25 m and wait for the hammerheads
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
Hold position at 18–24 m while hammerhead schools pass the plateau
Sunken mountains dived along either flank at about 24 m
Oceanic mantas and hammerheads over rock rising from 45 m
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An 18–35 m rock in open sand, rated expert to technical