When most people hear the words “sea snake,” they immediately think of highly venomous snakes that inhabit marine (salt water) environments, just part of the reason sea snakes are greatly feared by many people. Most people also believe that sea snakes are only found in the Indo-Australian regions and the South China Sea, but sea snakes are much more wide ranging than that. In fact, one sea snake, the yellow-bellied sea snake, ranges from Eastern Africa, throughout the Indian Ocean and thru the Indo-Australian region, across the great expanse of the Pacific Ocean and along the western coast of the Americas. Their range is one of the greatest ranges of any reptile species on Earth!
On Costa Rica tours with International Expeditions , I’ve seen this species numerous times and they are always a great joy to observe. The yellow-bellied sea snake is appropriately named — its belly is yellow and its back is black. These snakes are very laterally compressed, meaning very thin from side to side. The amount of yellow on the sides of the snake varies considerably between individuals, and many have beautiful undulations of zig-zag patterns where the yellow meets black. For aquatic animals, including some very familiar creatures like penguins, orcas, fishes of all kinds and sea snakes, the belly is light to provide camouflage from any creatures below them looking up. Likewise, the black or dark patterns on the back provide good camouflage from any predators above, especially when diving as most aquatic species have to dive to depths to acquire food. The yellow-bellied sea snake has a marvelous design and its tail is flattened and looks like a paddle. This species is basically an ambush predator that enjoys floating among debris (both natural and man-made trash) as this sort of flotsam attracts fish to shade of such objects. As a fish gets close to a motionless yellow-bellied sea snake, the snake quickly strikes. The venom is designed to immobilize prey very quickly, working on the nervous system of its victim.
At times, I have found yellow-bellies caught in the surf in areas like Manuel Antonio as well as in the Guanacaste area, both on Costa Rica’s Pacific coast. Once in the surf, they have difficulty getting back out beyond the breakers and at times find themselves washed up on shore. Here, they quickly perish as they cannot crawl on land and they overheat in the open sun of a hot beach. It is not advisable to pick up these creatures as their venom is quite virulent. I have worked with reptiles for over 40 years and I do pick them up and swim them out beyond the breakers to release. Many people feel that sea snakes have very short fangs and thus are not a danger to people. For this reason, I have selected one of my photos showing the size of the teeth on the yellow-bellied sea snake. They are quite large and can easily deliver a dangerous bite.
Naturalist Greg Greer  is a favorite among IE travelers, and has gained a reputation for his friendliness and good humor, along with his incomparable knowledge of natural history, photos and articles have been widely published in books and magazines, including Georgia Outdoor News, Bird Watcher’s Digest, Alabama Outdoor News, Riversedge and Southern Wildlife.