FWIW, I'll echo recceguy's sentiments about being careful. I fly into a semi remote part of western Nova Scotia to do fire duty every now and then and the snapping turtle population down there is huge, especially on the particular lake we stay at. The first time I saw one it was on the road and I thought, "Wow, neat, gotta get some pictures!"
Ignoring my coworkers advice I picked the critter up by the shell towards the back so I could avoid the legs flailing. To my utter shock this thing swung its head and neck out and just missed taking a good chunk out of my arm!! Turtle became frisbee and I got int he truck slightly shaken.
Later, when I related the story to some locals they told me that people have suffered broken fingers and toes from turtle bites during a swim. Urban myth? Maybe. But I know I saw enough of that one turtle's jaws to make a believer out of me.
Also, to get rid of them, the time is coming where they'll be looking to lay eggs. If you know where they normally nest you can lie in wait and pounce for the kill or trap. But don't go after them if they make it to the water.