tortises vs turtles

Question
what is the difference between a tortoise and a turtle?
And are there tortoises that live in water?

Answer
Turtle is a catch-phrase for all shelled reptiles, and the term used for aquatic and semi-aquatic turtles.

Tortoise technically refers to those turtles in the family Testudinidae- the 'true tortoises', which can be identified by  elephant-like front feet.

In Europe and in some other places, 'tortoise' also refers to the turtles that live on land but are not Tesudinidaes, like the American Box Turtles.

No true tortoise lives in water, but...
- There is a species of American Box Turtle that lives mostly in water- the rare Caohuilian Box Turtle in Mexico.
- In Australia, they refer to many species of aquatic turtles as 'tortoises'.