Overview
The Annulated Sea Snake (Hydrophis cyanocinctus), also known as the blue-banded sea snake, is one of the largest and most abundant true marine elapids in the tropical Indo-Pacific Ocean. Completely adapted to an oceanic lifestyle, this gracefully banded venomous predator never comes ashore, giving birth to live young at sea and utilizing specialized skin respiration to remain submerged for hours at a time.
Biology and Physical Characteristics
Hydrophis cyanocinctus features a long, laterally compressed body terminating in a paddle-like tail that functions as a powerful marine oar. Its coloration consists of a pale yellow, olive, or creamy base encircled by 45 to 70 distinctive dark blue-gray or black bands. As a fully marine reptile, it possesses valved nostrils that seal watertight when diving, sublingual salt glands that excrete excess sodium, and highly vascularized skin that allows it to absorb up to 25 percent of its oxygen directly from seawater.
Behavior and Ecology
Annulated sea snakes forage across murky coastal mudflats and rocky reefs down to depths of 30 meters, probing into crevices and holes to hunt eels and bottom-dwelling teleost fish. Possessing an extraordinarily potent postsynaptic neurotoxic venom designed to instantly immobilize thrashing marine quarry, they subdue prey with minimal struggle. Reproduction is entirely viviparous; females gestate embryos internally and give birth to 3 to 16 free-swimming young in coastal bays.
Conservation and Human Impact
Evaluated as Least Concern by the IUCN, the annulated sea snake maintains resilient populations across its extensive tropical range. The species is, however, frequently captured as incidental bycatch in commercial shrimp trawlers and artisanal gillnets throughout the Gulf of Thailand and Indian Ocean, where it is often harvested for leather, traditional medicine, and coastal culinary consumption.
Interesting Factoid
The annulated sea snake can breathe through its skin underwater, absorbing oxygen directly from the surrounding sea while diving for hours without surfacing for a breath of air!
Last updated: October 2026