Gen X here, too.

When visiting a great-uncle and aunt's horse farm that they had on mostly-wooded 100 acres (yep), we were kept away from the "crick" by being told there was "quicksand" there. Dunno about that, but there WAS some sucking mud that nearly stole a cousin's shoe when we realized we'd gotten too close to said "crick". Oh, the panic, lol.

That waterfall scene in Christopher Robin really did hit home, ha. That dangerous "crick" was probably no deeper and wider than that.