Why do sea snakes need to drink freshwater?

Why do sea snakes need to drink freshwater?

Despite spending their entire lives in the ocean, sea snakes face the same physiological challenge as terrestrial animals: the constant need for hydration. While they are highly adapted to marine life, their bodies cannot process the extremely high salt content of seawater.

The Problem with Seawater

If sea snakes were to drink seawater, the high concentration of sodium and chloride ions would overwhelm their internal organs. Like marine mammals and seabirds, snakes lack the specialized, highly efficient salt glands (like those found in marine iguanas or sea turtles) that would allow them to excrete large amounts of concentrated salt without expending critical bodily water.

Where Do They Find Freshwater?

Because of this limitation, sea snakes must rely on sporadic rainfall. During heavy tropical rains, a layer of fresh, less dense rainwater temporarily floats on top of the denser saltwater surface of the ocean. Sea snakes actively seek out and drink this "lens" of freshwater to rehydrate. Research has shown that sea snakes actually become dehydrated during prolonged dry periods and will actively seek out freshwater sources at the ocean's surface as soon as it rains.