Dos Amigos Grande
Depth is the range from the top of the site to its usual maximum; "recommended cert" is the mainstream-agency level operators usually ask for, not a legal rule. Currents and visibility change daily — treat everything here as planning ranges.
The larger of the two friends - a pair of rock islets off Cocos's southwest corner - carries the island's most photogenic piece of architecture: a broad arch punched through the pinnacle at about 20 m, big enough to frame a diver, a shark, or on charmed days both. Hammerheads round the outside in the current while whitetips carpet the ledges, and marbled rays hold on the rubble below the arch like parked aircraft. The exposure is real; when swell wraps the corner the surge through the archway commands respect. Divers work the down-current side, shoot the arch against the blue, and finish drifting off the rock.
The moment you come for: The 20 m archway, hammerheads on the outside edge, marbled rays in the rubble
Topography: Steep rock with a large natural archway around 20 m
Know before you splash
Hazards: Surge through the arch, current at the corners, blue-water pickups.
Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).
Who you'll meet
Marbled Ray
Scalloped Hammerhead
Silky Shark
Whitetip Reef Shark
For photographers
Wide angle: ★★★★★ · Macro: ★☆☆☆☆ — editors' 1–5 rating of what this site gives each style of shooting