Cocos Island sharks & rays

Scalloped hammerhead Sphyrna lewini

Critically Endangered on the IUCN Red List, and the shark most divers come to Cocos to see. The waters between Cocos and the Galápagos are a migration corridor for it (Mission Blue).

Key marks: The head is flattened into a hammer with a scalloped front edge: a notch in the middle and a shallow scallop either side of it. Eyes at the very tips. Tall, strongly curved first dorsal fin and a small second dorsal. Bronze-grey above, pale below. In open water you usually get the silhouette from below before any colour, so go by the shape of the head.

At Cocos: Schools of 200 or more have been reported, mostly females averaging about 2.4 m (SEE Turtles 2024), and DAN describes schools of hundreds over Bajo Alcyone. Cleaning stations at Manuelita, Dirty Rock, Punta María and both Dos Amigos, the Dos Amigos stations at about 30 m (DAN). Densest in the wet season, June to November (Liveaboard.com).

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Whitetip reef shark Triaenodon obesus

A slim reef shark with white tips on the first dorsal fin and the upper tail lobe. It spends much of the day resting on the bottom, in caves and under ledges.

Key marks: Small and slim, with a short, blunt snout. A white tip on the first dorsal and on the upper lobe of the tail, often on the lower lobe too. The pectoral fins are plain. Usually lying still on sand or under a ledge during the day. Do not confuse it with the silvertip, which is much bigger, has white edging on all its fins, and does not rest.

At Cocos: The most common shark at Cocos (SEE Turtles 2024). By day it rests on sand and in crevices, for example in the swim-through at Submerged Rock (DAN). At night dozens to hundreds hunt together over the reef at Manuelita and in Chatham Bay (DAN; Blue Water Dive Travel).

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Galápagos shark Carcharhinus galapagensis

A reef shark of clear water around oceanic islands, commonly about 3 m, with a tall first dorsal fin. Easily confused with the silky shark; see the Shark ID page.

Key marks: Stocky and plain grey-bronze, with a broad, rounded snout and a heavy look to the head and shoulders. The first dorsal is tall and upright and starts roughly above the pectoral tips. A low ridge of skin runs along the back between the two dorsal fins. No strong dark or white fin markings. Works the reef and the walls, and will come in close.

At Cocos: Visits the cleaning stations at Dirty Rock and Punta María, where close passes are common (DAN; SEE Turtles 2024). One stayed with a group for a whole night dive at Manuelita Shallows (Blue Water Dive Travel).

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Silky shark Carcharhinus falciformis

A slender open-water shark, typically about 2.5 m, named for its fine, smooth skin. Listed as Vulnerable.

Key marks: A very small second dorsal fin with a long, thin trailing tip is the best single mark. The first dorsal is low and rounded and starts behind the pectoral fins. Long, narrow, sickle-shaped pectorals, dusky on the underside of the tips. Slim and smooth, bronze above and white below, usually out in the blue and in numbers.

At Cocos: Reported at Manuelita, Dirty Rock and Bajo Alcyone (DAN). Described as an occasional sighting on a 2024 expedition (SEE Turtles 2024).

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Tiger shark Galeocerdo cuvier

A large shark with a blunt, square snout. Young animals have dark vertical stripes that fade with age.

Key marks: A very blunt, square snout on a broad head. Dark vertical bars and blotches down the flanks, strong on young animals and faded on big adults. Heavy-bodied, with a long upper tail lobe.

At Cocos: Reported more often in recent years. Two were seen at Manuelita in November 2016, the larger about 4.5 m long (Blue Water Dive Travel). In 2024 they were seen cruising the sandy edge of the reefs, including a juvenile in the Coral Garden (SEE Turtles 2024).

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Silvertip shark Carcharhinus albimarginatus

A large grey shark with bright white edges on the tips of its fins, which makes it easy to pick out from the grey sharks around it.

Key marks: White edging on almost every fin: the tip of the first dorsal, the tips and trailing edges of the pectorals, and the tail. Larger and bulkier than the whitetip reef shark, with a longer snout, and it keeps cruising off the reef instead of resting on the bottom.

At Cocos: Sometimes seen at Silverado, the site named after it (DAN), and at Small Dos Amigos (Blue Water Dive Travel). An occasional sighting (SEE Turtles 2024).

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Whale shark Rhincodon typus

The largest fish in the world, a filter feeder that is harmless to divers. Listed as Endangered.

Key marks: Unmistakable. Very large, with a broad flat head and a wide mouth right at the front of the snout rather than slung underneath. Dark grey-blue with a chequerboard of pale spots and bars, and three ridges running the length of each flank. The spot pattern is unique to each animal, which is how researchers tell them apart.

At Cocos: Visits the offshore seamounts and is reported more often at Bajo Alcyone than at any other site (DAN). Most likely from August to October, late in the wet season (Liveaboard.com). An occasional sighting (SEE Turtles 2024).

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Giant oceanic manta Mobula birostris

The largest ray, with a wingspan up to about 7 m. It comes to cleaning stations to have parasites removed.

At Cocos: Occasional fly-bys at Manuelita (DAN); one was seen there with dolphins hunting jacks in November 2016 (Blue Water Dive Travel), and several were seen in August–September 2024 (SEE Turtles 2024).

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Marbled ray Taeniurops meyeni

A very large stingray that is common at Cocos, though it is not a species of every Eastern Pacific island.

Key marks: A broad, rounded, thick disc, grey with dense dark mottling, and a tail shorter than the disc with a deep fin fold underneath. Usually resting on sand or under ledges.

At Cocos: Common; females can be more than 2.7 m long (SEE Turtles 2024). Reported at Manuelita, under the arch at Big Dos Amigos at about 21 m, and on top of Bajo Alcyone (DAN); three large ones were seen at Submerged Rock in 2016 (Blue Water Dive Travel).

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Pacific eagle ray Aetobatus laticeps

A spotted eagle ray that flies along in a steady glide, with a pointed head and a long tail.

At Cocos: Several were seen gliding over sand in 2024 (SEE Turtles 2024). Eagle rays ride the current through the Channel between Cocos and Manuelita (SEE Turtles 2024), and are reported at Dos Amigos and Dirty Rock (DAN; Blue Water Dive Travel).

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