how do you tell the difference between aquatic turtles if they're a boy or a girl?

Answer 1

Depends on the kind of turtle. Some turtles it is based on back claw size and shape, some it is tail shape and size. www.turtleexchange.smfforfree.com has the most information I have ever seen on turtles and other pets. They have people who own several different types of turtles and can tell you everything you need to know. Give it a try.

Answer 2

Male aqua turtle’s tail is short and stubby. The female’s tail is long and sharp. For reproductive purpose the males underside is curved and female have flatter undersides.

Answer 3

the tail. female=long, "sharp"
male=short, stubby

also, the underside of the males is curved inwards for reproductive purposes. females have flatter undersides