Evolution is a fascinating process driven by adaptation. When it comes to reptiles and mammals, their movements have evolved based on their respective environments. While many reptiles are capable of swimming, their swimming technique is similar to their land movement, utilizing side-to-side body movements for propulsion. Crocodiles, for example, demonstrate this sinuous motion in water. However, reptiles are generally less efficient in terrestrial locomotion.

Mammals, on the other hand, have spent a significant amount of time adapting to life on land. Their movements have become distinct from reptiles, with limb placement below the body for efficient terrestrial locomotion. The lateral movements of their spine are primarily used for turns rather than straight-line locomotion. Cheetahs are a great example of this adaptation, as their spine vertically curves during high-speed chases, allowing their rear feet to reach forward past their chest.

When mammals swim, they utilize their limbs for propulsion, and their spinal movements during swimming involve vertical bending. Observing a dog swim reveals the use of limb paddling rather than side-to-side movements. Otters and seals also exhibit this vertical propulsion in water. Dolphins take this adaptation further, deriving thrust from vertical moves. This adaptation from terrestrial mammals is responsible for these changes in swimming techniques.

In summary, the unique movements and adaptations in swimming between reptiles and mammals can be attributed to their evolutionary history and the environments they have adapted to over time.