Imagine yourself in total darkness, on a reef, hundreds of miles from any major land. Your eyes are glaring into the endless blackness as your seemingly insignificant light beam frantically scans around, only catching the refraction of hundreds of pairs of silver eyes. Then, all of a sudden, you notice that you’re completely surrounded by hundreds and hundreds of White Tip sharks that are scanning the reef in search of prey. Many times they come close enough to rub against your body.

Now, imagine clinching to the top of a lonely seamount that sharply rises from the seafloor hundreds of feet below. A swift ocean current is attempting to rip you from the rock as you stare into the cobalt blue darkness. Faintly, off in the dark gloom, you’re eyes make out a dark shadow approaching. Suddenly, a single ten-foot Hammerhead shark approaches. It’s close enough for you to see your reflection in one of its deep black eyes. As the wondrous creature passes, you turn your attention back into the deep blue darkness. Off in the distance you see another dark shadow, then another, and another. Suddenly, the whole ocean around you comes alive as hundreds of large schooling hammerheads engulf the seamount. In awe, you find yourself flattened tight against the cold rock in a futile attempt to camouflage yourself in hopes that none of these sharks consider you as a potential meal. As quickly as they appeared, the large school fades and disappears back into the deep blue abyss, leaving you unscathed and alone with only the memory of this breathtaking experience.


This is Cocos Island!

Classified as one of the worlds best underwater locations, Cocos Island, located 331 miles into the Pacific Ocean, off the western coast of Costa Rica, provides experienced divers with an unforgettable, once-in-a-lifetime experience.

Cocos Island is located five degrees north of the equator and is the most northern island in the Galapagos chain. Established as a world preserve in 1997, the whole island and its surrounding waters are protected from any commercial fishing or harvesting.

Our adventure started with the Cocos Aggressor, the Okeanos, a 110-foot custom dive vessel, who holds one of the few permits that enable divers to experience this truly amazing destination. The boat ride from the west coast of Costa Rica to Cocos takes around 36 hours. Once the Okeanos arrives, it’s possible to hide away in several protected areas and out of any rough sea conditions. The amount of sea life surrounding the island and its underwater pinnacles is truly amazing. Every dive provides sightings of schools of fish in the thousands, dozens of Marble rays, and hundreds of white tip sharks.


Ron Benson invited ADM staff writer Jim Rozzi and myself for a journalistic view of Cocos on a special rebreather only charter. Eighteen certified rebreather divers from the U.S. and Canada joined the charter with several different types of rebreathers, including the Megladon, Inspiration, Kiss, Drager, and the RB80.

The reduced amount of bubbles, elimination of noise, longer bottom times, and increased depth durations enabled the divers to interact much closer with the marine life without being conceived as something foreign. Standard gas fills on the Okeanos went from 80 cubic feet per diver, per dive, to a 10 cubic foot top-off of oxygen and air diluent once a day. In total, the whole group of 18 divers used less than two oxygen bank cylinders for the duration of the trip.

While the Okeanos stayed anchored in the protective cove, the rebreather divers were shuttled to the dives sites on smaller vessels called Pangas. Once on the site, a time duration of around 60 to 100 minutes was set for the divers to return to the surface. Unlike a standard aluminum 80 cubic foot cylinder, many of the closed circuit rebreathers had three to five hour dive duration on less than 20 cubic feet of oxygen and diluent.


Diving is somewhat different in Cocos compared to a normal reef excursion. Being famous for it’s large pelagic inhabitants, the focus of most dives was to interact with as many of these creatures as possible. Many times you found yourself perched on the edge of a wall like a lonely crab staring off into the vast blue void waiting patiently for any dark shadows to appear in the distance. Thousands of Horse Eyed Jacks, cigar minnows, and an enumerable amount of reef fish passed within inches, seemingly unaware of your existence.

This is the closest to being a real fish you’ll ever achieve. The only noise you would hear was the occasional piston sound of your injector automatically maintaining the oxygen set point of 1.4 PO2 in the breathing loop. It was so quiet, that you started noticing that the ocean is really an extremely noisy place. Muffled sounds of waves breaking against the rocks, a pinging noise as the sand shifted along the ocean floor, grunts from a multitude of reef fish, whistles and song from distant marine mammals, along with a maraud of indescribable sounds echoed throughout the seas.

The wildlife is so extreme in Cocos that almost anything can appear in front of you from the deep blue abyss. When it does appear, it swims close enough for a one-on-one personal experience, and then disappears back into the darkness, leaving you with a visual experience of a lifetime.


The Okeanos Aggressor

Built by Codecessa shipyard in Viareggio, Italy, the 110-foot, 24-foot beam, all-steel vessel has a range of 1,500 nautical miles. It departs biweekly from the port town of Puntarrenas, Costa Rica.

Equipped with the most modern electronics, the Aggressor Okeanos has nine guest staterooms, each with double and single berths. All cabins are fully carpeted, air conditioned, and have a private bath and in-room vanity. The main salon is furnished for comfort and relaxation. Stocked with a large variety of DVD’s, videos, books, and magazines help make the long crossing entertaining. The Okeanos has multiple sun decks and a wet bar for those divers who wish to relax and take in some rays.

The large dive deck provides each diver with his or her own personal location to set-up and store equipment. Cylinders are conveniently filled with either air or Nitrox between dives by the staff gas blenders. The dive deck also contains special protected tables and rinse tanks for video and photography equipment.

For more information on the Aggressor Fleet, go to


This is Cocos Island from Aggressor Adventures on Vimeo.