Generally it depends on the species. However if raised fully aquatic they need a floating island for when they occasionally get the urge the come out of the water if only briefly. They are air breathers with a large lung capacity considering their size. They swim to the surface a quickly take a gulp of air before either just dropping to the bottom or swimming around below the surface. Some species require a hibernation period others require a land based period to induce breeding.
The three species I keep are raised fully aquatic. I am acquiring four of these tomorrow with hopes of breeding them in a year or two. I have eggs from all three species I keep now gestating.