The combination of warm tropical waters and the upwelling, nutrient rich, cool Humboldt waters allow the Galapagos Islands to support a wide array of marine life. These waters are home to sharks, sea turtles, sea lions and 306 varieties of fish, 25% of these fish are endemic. There are few coral reefs in these waters, instead the crevasses in the lava provides the function of a reef in other environments. Smaller fish live protected within the crevasses coming out to feed, and invertebrates make their home in the lava. The marine food chain and life is established around the lava as larger fish live near the lava area where they feed on the smaller fish.

Viewing the Marine Life
Diving in the Galapagos has been rapidly increasing in the last few years. These trips visit some of the remote island areas like Darwin and Wolf where land visits are not possible, but diving is exceptional. The highlight of these trips is viewing the Galapagos' big animals including Whale Sharks, Hammerheads and Manta Rays while Sea Lions, Hammerheads, Galapagos sharks, Eagle and Golden Cow Rays and vast shoals of reef fishes can regularly be seen on diving day trips from around Santa Cruz island and the nearby central islands. Natural history cruises also allow visitors to have a glimpse of life under the sea. These trips offer snorkeling excursions in place like Devil's Crown a submerged volcano, which offers an experience similar to swimming in a tropical fish tank or to Academy Bay where swimming with a colony of sea lions is an opportunity not to be missed.

Sea Turtles
The Pacific Green Sea Turtles spend most of their lives in the ocean. Adult shells grow to 3 ft (1 m) in length with a body weight of up to 400 lbs. (180 kg). These cousins to the tortoise mate in the waters near the Galapagos and are often seen near Caleta Tortuga Negra on Santiago . Males never leave the sea, but females come ashore on beaches to nest and lay eggs on several of the islands.

Green Sea Turtles are an endangered species. Turtle eggs are eaten and pigs and rats frequently destroyed their nests. Hawks, herons, mockingbirds, and frigatebirds prey on young hatchlings. If these young turtles make it to the sea, fish and sharks hunt them.

Whales & Dolphins
In the 19th century whale oil was a main source of energy around the world. Whales, dolphin and porpoises all have a blubbery layer of fat around their body. This blubber allows them to stay warm in cold waters and gives them extra energy during long migrations. It was this blubber that the whalers would seek; they would melt it down creating whale oil. The Galapagos Islands were the center of whaling in the Pacific Ocean .
The practice of whaling has stopped and many of these large mammals still visit the Galapagos during their migrations. Whales, Dolphin and Porpoises make up a family of Cetaceans; the family can be divided into two parts those with teeth and those with Baleen Plates.
Baleen Plates are large, horny triangular pieces of whalebones occurring on the upper jaw of toothless whales. The Baleen grows from 2 - 12 ft (.6 - 3.6 m) rows along the gums of the upper jaw. The whales push water through the plate allowing them to feed on plankton, shrimp, sardines and other small creatures. Those animals with Baleen Plates are the larger whales including the Blue, Finback, Sei, Humpback, Bryde's and Minke ; all which can be seen in the Galapagos waters.
Toothed Cetaceans are a more diverse group including the large Sperm Whale, the Orca, the False Killer Whale, Short Finned Pilot Whale , and several Dolphins. All are frequently seen in the waters surrounding the Galapagos. The Bottled Nosed Dolphin and White Bellied Dolphin live in these waters. Bottled Nosed Dolphins can be seen riding the bow wave in front of boats. White Bellied Dolphin can be seen in schools of more than 100.