Because of its position at the intersection of three ocean currents, Isla del Coco is home to a staggering array of fish and other sea creatures. Fifty-eight of the marine species that dwell here are endemic to the island. Divers are likely to see manta rays, schools of mobula and marble rays, angelfish, Moorish idols, damselfish, pufferfish, jacks, tuna, snapper, sailfish and pompano, among others. These waters are also frequented by bottlenose dolphins, sea turtles, silky sharks, whale sharks, white-tip sharks, silver-tip sharks, Galapagos sharks, and most famously, enormous schools of hammerheads. Sea creatures you may see on the ocean floor include flower coral, orange cup coral, crown of thorns sea stars, giant oysters, harlequin shrimp, red-lipped batfish, lettuce sea slugs, octopus, club-tipped anemones, frogfish and zebra morays.
Because the waters around Isla del Coco are undisturbed by human activity, it is easy for divers to observe these creatures in a completely natural state. There are also several “cleaning stations” around the island where large fish (including hammerheads) stay put as they allow smaller fish to rid them of parasites.
There are at least 17 different dive sites around the island, with dives ranging from 20 to 130 feet in depth. One well-know spot is Dirty Rock, where intriguing rock formations shelter dozens of different marine creatures, including many large pelagic species, and where bigeye jacks school by the thousands. Another famous site is the Bajo Alcyone seamount, where schools of hammerheads traveling back and forth from far-off feeding grounds, and where you can find several other species of sharks, rays and large fish.
There are only two companies in Costa Rica that conduct excursions to Isla del Coco: Undersea Hunter and the Aggressor Fleet (although other tour companies sometimes work in conjunction with these two) Trips with Undersea Hunter last 10 days and cost $4,495 or $5,695 per person depending on which boat you go on. This includes meals and some equipment. It does not include the $245 park fee. Tel: US 1-800-203 2120, CR 2 228-6613, Fax: CR 2 289-7334, E-Mail: info(at)remove-this.underseahunter.com, URL: www.underseahunter.com/uh.htm.

The Okeanos Aggressor takes trips of eight or 10 days for $2,935 to $4,235 (prices are per couple). Meals and some equipment are included. Tel:(800) 348-2628 / +1-985-385-2628, E-mail: okeanos(at)remove-this.aggressor.com, URL: www.aggressor.com.
Due to park regulations, dive groups are limited to 10 people and must be supervised by a dive master. Both companies include excursions to the island itself as well for hiking and swimming.