Originally posted by PakaNoHida:

What turtles?

There are no turtles in game. There are some leviathans in the water, but no turtles, are you modded?

That image he linked is a Leviathan. As to what happens... there's only one way to find out, I guess rofl. Set up a portal nearby, make a new character, build a Raft (or a Karve, if you've got four Bronze you wouldn't mind losing), give him an Antler Pick, and give it a shot!