Iguanas are large, terrestrial reptiles typically associated with basking in trees or on rocks. Yet, many species possess a surprising and effective ability to navigate aquatic environments. This capability is a deep-seated survival mechanism for some, and a defining characteristic for others. A significant number of iguana species are considered strong swimmers. Their capacity to move through water allows them to escape predators, disperse to new territories, and, in one unique case, forage for food.
Measured Swimming Speed
The measurable swimming speed of iguanas is modest compared to their rapid movements on land, where some can sprint over twenty miles per hour. When iguanas enter the water, they are built for efficient, quiet movement and quick bursts, not sustained high velocity. For strong-swimming species observed during flight responses, the maximum burst speed generally falls within a range of 0.5 to 1.6 kilometers per hour (approximately 0.3 to 1 mile per hour).
Sustained cruising speeds are slower, often measured at around 0.45 meters per second. This speed is typically employed as a short-term escape tactic, allowing the reptile to rapidly put distance between itself and a perceived threat. Once the immediate danger has passed, the iguana slows down to a more energy-efficient pace, relying on submersion and camouflage rather than raw speed to remain safe.
Species That Dominate Aquatic Environments
The iguana family contains a wide variety of species, but two stand out for their differing relationships with water: the Green Iguana and the Marine Iguana. The Green Iguana (Iguana iguana) is primarily an arboreal species, but it is frequently found near water in its native Central and South American habitats. Its swimming is largely a defense mechanism; when threatened, it will drop from a tree branch into the water below and swim away to safety.
The Marine Iguana (Amblyrhynchus cristatus), endemic to the Galápagos Islands, is unique as the world’s only lizard that actively forages in the ocean. This species has fully embraced the aquatic environment, driven by the need to graze on marine algae growing on submerged rocks. Unlike the Green Iguana, the Marine Iguana swims as a necessity for survival, dedicating a significant portion of its day to ocean activity. This ecological distinction means the Marine Iguana has a higher tolerance for cold water and specialized glands to expel excess salt ingested during feeding.
Propulsion and Underwater Capabilities
Iguanas move through the water using a specialized form of locomotion that maximizes the power of their long, muscular tails. To reduce drag and maintain a streamlined profile, the animal holds its four limbs tightly against the sides of its body. The legs are generally not used for propulsion.
Movement is achieved almost entirely through powerful, lateral undulations of the tail, which acts as a sculling oar. This side-to-side motion pushes water backward, generating the forward thrust needed to propel the body. Their aquatic abilities include impressive breath-holding, a skill used for predator evasion and foraging. Green Iguanas can remain submerged for 30 to 45 minutes, while the Marine Iguana can remain underwater for an hour or more in colder temperatures.