In my turtle pond, which has sloping sides, 'coons (and cats, too, I'm convinced) just wade in. There are overturned pots for the fish to hide in, and they're fairly heavy. But the 'coons just take their time, uproot everything, overturn the pots, and are good at getting every fish.
Last time, out of seven fish, they got five. And dint' even bother to eat them ... just an eyeball here, a half a head there, and left the bodies of the fish in the pond or on the shore nearby.
And, yes, they will get your turtles, too, especially the babies and they will also dig up the unhatched eggs. Now when I notice a fresh nest, I dig up the eggs and move them to a protected pen, and all my babies stay in there, too, as it has a tight fitting hardware cloth mesh cover.