Many reptiles are adapted for aquatic habitats. Crocodilians (such as the American alligator Alligator mississippiensis), the marine iguana (Amblyrhynchus cristatus) and Philippine Sailfin lizard (Hydrosaurus pustulatus) are all examples of reptiles that can be found in aquatic environments. We hypothesize that organisms adapted for an aquatic lifestyle should have anatomical adaptations related to that lifestyle. The aquatic reptiles named above will be compared to the green iguana (Iguana iguana) that primarily inhabits terrestrial environments. We will examine the skeletal and muscular anatomy of these organisms to determine the anatomical adaptations, if any, that are present in relation to an aquatic lifestyle. Although these adaptations may be found throughout the body, our research will focus on the tail, as the tail is the primary structure used for locomotion in many aquatic organisms.