[[I don’t know if they would actually grab a human foot or something that big unless in self-defense. No idea. ]]
They bite at anything within reach- doesn’t matter how big- and when they get ahold of you they don’t let go easily- their jaws are like a vice- and the turtles are shockingly fast when they snap their heads out to strike too- and they can bite backwards as their necks are quite long- Best not to eaven mess with them if possible-They can sever fingers and toes-
They were quite the thieves of stringers of fish though... if you didn't keep your eye on the bluegill on your stringer the next time you glanced over you could see the stringer being pulled into deep water along with your catch. Or you'd pick up your stringer and find a fish or two with big bites taken out of them.
When there were too many they were a real pain so we'd thin them out by catching them with a lure and a three prong rake and take them to a neighbor who liked turtle soup. Most of the time they were OK since they preferred bluegill to other fish and you can never overfish the bluegill.
Bluegill can overpopulate a pond to the point that none of the fish ever grow big, so having them thinned down was a benefit to other species and improved the size of the bluegill too.