But seriously, folks! Why do sea turtles swim using only their flippers while their freshwater cousins paddle with all 4 legs?
Freshwater turtles have legs while sea turtles have flippers. ST have to swim long distances. They are swimmers. Freshwter turtles just have to putz around a lake or pond.
Note that seals have flippers while otters have legs. Same sort of dichotomy.
Don't know if that is it, but sounds good to my nonexpert ears.