You’ve probably been wondering about this:
Turtle— Spends most of its life in the water. Turtles tend to have webbed feet for swimming. Sea turtles (Cheloniidae family) are especially adapted for an aquatic life, with long feet that form flippers and a streamlined body shape. They rarely leave the ocean, except when the females come ashore to lay their eggs. Other turtles live in fresh water, like ponds and lakes. They swim, but they also climb out onto banks, logs, or rocks to bask in the sun. In cold weather, they may burrow into the mud, where they go into torpor until spring brings warm weather again.
Tortoise— A land-dweller that eats low-growing shrubs, grasses, and even cactus. Tortoises do not have webbed feet. Their feet are round and stumpy for walking on land. Tortoises that live in hot, dry habitats use their strong legs to dig burrows. Then, when it’s too hot in the sun, they slip underground.
Terrapin— Spends its time both on land and in water, but it always lives near water, along rivers, ponds, and lakes. Terrapins are often found in brackish, swampy areas. The word terrapin comes from an Indian word meaning “a little turtle.”