Rattlesnakes are highly capable swimmers, a common question for those living near water sources where these snakes are present. They can navigate through water with surprising efficiency, though they are fundamentally terrestrial creatures. They are not truly aquatic and lack the specialized adaptations of water-dwelling snakes. A rattlesnake will typically avoid submerging its body and only enters the water to cross a body or escape a threat.
Rattlesnakes and Surface Swimming
Rattlesnakes are naturally buoyant, allowing them to float and move easily across the water’s surface. This buoyancy is largely due to their elongated lung structure, which acts as a floatation device. They propel themselves using lateral undulation, a winding, S-shaped motion also used for slithering on land. While swimming, the snake keeps its entire body afloat, holding its head and rattle clearly above the waterline. This position allows them to breathe continuously and maintain a clear view of their surroundings.
Rattlesnakes do not typically swim to hunt, as their primary prey consists of rodents and other small terrestrial animals. Their ability to cross water enables them to access new foraging grounds or escape from immediate danger. Their scales and the water’s surface tension help support their body. This means they expend little energy to stay afloat and can swim for extended periods.
Why Rattlesnakes Do Not Submerge
Rattlesnakes are air-breathing reptiles and lack the physiological traits necessary for prolonged underwater existence. Unlike fully aquatic reptiles, they cannot extract oxygen from the water through specialized skin or gill-like structures. Any time spent submerged requires them to hold their breath, making sustained diving a non-viable behavior. Although they can hold their breath briefly to evade a threat, rattlesnakes do not regularly submerge themselves. Their anatomy is not designed for underwater hunting or movement, and they would quickly become exhausted.
Furthermore, the risk of chilling in cooler water temperatures presents a danger to these exothermic animals. The primary function of their single, elongated lung is to provide the buoyancy needed to float effortlessly on the surface. Fighting that natural buoyancy to stay submerged requires a significant and energy-intensive effort. While they are technically capable of a brief dive, sustained underwater swimming is not a natural part of a rattlesnake’s behavior.
Mistaken Identity: Rattlesnakes vs. Water Snakes
Confusion often arises because rattlesnakes are frequently mistaken for other, more aquatic species of snakes. Rattlesnakes belong to the genera Crotalus and Sistrurus and are primarily land-dwelling vipers. The snake most commonly confused with a rattlesnake in the water is the Cottonmouth (Agkistrodon piscivorus), also known as the Water Moccasin. The Cottonmouth is a semi-aquatic pit viper found in the southeastern United States that spends much of its time in or near water.
While both the rattlesnake and the Cottonmouth tend to swim with their entire bodies floating on the surface, the Cottonmouth is much more likely to submerge to hunt for fish and amphibians. This aquatic behavior is a significant difference from the rattlesnake, which only uses water for crossing or escape. Non-venomous water snakes, such as those from the genus Nerodia, typically swim with most of their bodies submerged, with only their heads above the surface. This contrasts with the highly buoyant swimming style of the rattlesnake and the Cottonmouth, whose entire bodies float like a log.