The most common native mammal that travelers see during their visit to the Galapagos is the Galapagos Sea Lion, a subspecies of the Californian Sea Lion. An estimated 50,000 live in the Galapagos. The territorial bulls, which can reach up to 7 feet in length and 800 pounds, are quite aggressive and have been known to chase swimmers out of the water. They have also been known to bite if harassed, so visitors are advised to give them there space. The females and the young, on the other hand, are social, curious, and often swim playfully around snorklers and scuba divers.

Though they appear somewhat clumsy on land, sea lions are remarkably fast and agile in the water, skillfully maneuvering in pounding surf and past sharp lava and rock formations.