I've swam in every confeivable swamp and river nastiness north of the Mason/Dixon line......gars, snappers, snakes, 75#+ catfish.....Never had a water critter come after me.
I've startled big snappers and even had one basically swim up into my lap as we were draining a pond, once....
He beat a hasty retreat rather than show any aggression.

Now the ones I've cornered on land show a different temperament altogether.

That's been my experience.

Snappers are pretty tough on other wild critters, and waterfowl, especially, fwiw.