I too found this bug. I called it "dresser dashing." It can be used to super-easily get out of bounds, especially on water (and you can push NPCs out of bounds, too). It's not as easy to get back into bounds once done, though. Also, when you're out of bounds, unsurprisingly, a lot of pathfinding stuff breaks. It can also break simply from the speeds of the thing.
Dresser dashing also allows you to move your character or other characters around in certain cutscenes, which can break them or allow you to get out of bounds in a different way. 
Witch of the lake, what is your wisdom?