While most lizards are primarily terrestrial, a subset of species has evolved adaptations to inhabit aquatic or semi-aquatic environments. They demonstrate a broad spectrum of reliance on water, from those that spend nearly their entire lives submerged to others that utilize water primarily for escape or hunting.
Lizards and Their Water Habitats
Lizards exhibit varying degrees of interaction with water. The marine iguana ( Amblyrhynchus cristatus) stands as the sole modern lizard species that is truly marine, foraging exclusively in the ocean for algae. These reptiles are found only in the Galápagos Islands, navigating coastal waters to feed.
Many other lizards are semi-aquatic, spending considerable time both in water and on land. The basilisk lizard, known as the “Jesus Christ lizard,” can run across the surface of water for short distances to escape predators. These lizards are also proficient swimmers and can remain submerged for up to 30 minutes. The water monitor (Varanus salvator), a large lizard found across South and Southeast Asia, is another example. Water monitors are powerful swimmers, using water for hunting prey, escaping threats, and regulating body temperature.
Beyond these, many lizards are water-dependent or riparian, meaning they live near water sources but are not primarily aquatic. These species rely on water for needs such as hydration, a source for prey, or as a refuge from predators.
How Lizards Adapt to Water
Lizards that thrive in aquatic settings possess biological and behavioral adaptations. Physical modifications include body shapes, such as the flattened tails of marine iguanas and water monitors, which act as rudders for efficient propulsion through water. Some aquatic lizards, like the basilisk, have webbed feet that increase surface area, aiding in both swimming and their ability to run on water. Many species that dive also have specialized nostrils that can close to prevent water entry.
Physiological adaptations enable lizards to manage the challenges of aquatic life. Marine iguanas, for instance, possess specialized salt glands located near their nostrils. These glands filter excess salt ingested from seawater and algae, which is then expelled through a “sneezing” process. Some aquatic lizards exhibit oxygen utilization, allowing them to hold their breath for extended periods underwater; marine iguanas can remain submerged for up to an hour, and water monitors for around 30 minutes. The water anole can even create an air bubble on its hydrophobic skin to “rebreathe” oxygen while submerged.
Behavioral adaptations include diving, a common behavior allowing aquatic lizards to access underwater food sources or evade threats. Swimming techniques vary, with some primarily using tail undulation for propulsion and others relying more on limb paddling. The basilisk lizard’s running-on-water behavior is a rapid, coordinated movement of its webbed feet, creating temporary air pockets that support its weight on the surface. Many aquatic species also use water as a thermal regulator, cooling down after basking in the sun.
Common Misunderstandings
A common misconception involves distinguishing lizards from amphibians like newts and salamanders. Lizards are reptiles, characterized by dry, scaly skin and a reliance on air breathing, even in aquatic species. Amphibians, conversely, typically have moist skin and often undergo aquatic larval stages, possessing gills for underwater respiration.
Another point of confusion arises with other large aquatic reptiles. Crocodilians, which include alligators and crocodiles, are not lizards. While both are reptiles, crocodilians belong to a separate taxonomic order, Crocodilia, and are not closely related to lizards, which are part of the order Squamata. Crocodilians have distinct anatomical differences, such as the structure of their teeth and the presence of bony plates within their skin.
The vast majority of the over 7,000 lizard species worldwide are terrestrial. While some have adapted to aquatic or semi-aquatic lifestyles, these represent a smaller proportion of the total lizard diversity. Even those highly adapted to water, such as the marine iguana, still require land for basking, nesting, and other terrestrial activities.