A .22 LR will penetrate Red Eared Slider shells.
Back when I was about 10, I sat on the bank of a stock tank at the deer lease and shot turtles for many hours and several days.
A few days later, there were what seemed like thousands (probably several 100) dead ones washed up on the bank.
I agree...a .22L will penetrate the shell of a painter or a slider. It would probably just cause a snapper to move somewhere else for a while.
Shooting on water, defies my common sense.