Locomotion is crucial to the survival of species. It enables organisms to hunt, hide, build shelter or find their mates. Principles of locomotion are established on hard ground, air or water; however, locomotion on complex, uneven terrain is less understood. I am interested in studying the kinematic principles that govern gait transitions of animals that live at the water-land interface. Varying species of reptiles, mammals or fish transition between these environments on a daily basis, using specialized limbs for either water or land propulsion. I hypothesize that a minimum set of functional morphological features are retained in these species that allow for the gait transitions as they cross from water to land. I use high speed video and 3D kinematic tracking combined with a mathematical dynamical system theory and physical models to analyze the gait transitions. I chose to study marine and freshwater turtles as they live in water as well as on land and make use of both environments. Studying gait transitions allows for better understanding of the evolution of locomotion and has valuable applications for robotics.