Yeah, they can swim, but they don't rely on a body of water like other turtles. There's no need to do anything with them unless they're in the middle of a road.
I talked him into just letting it go. Poor little fuck had been hit by a car at some point (he was healing well), no need in messing with him any more.
My homie's dad : I found a turtle, I'm gonna throw it in the pond.
Me: that's a box turtle, don't do that.
Him: yeah, it's a turtle, they live in water
Me: ....