I'm still trying to find the cause of the swim transition bugging out. I think it's related to a computer with low memory or a slower CPU. The game needs to be optimized and something in the swim transition seems to be framerate-dependent. :/
The way you've described the broken race, it sounds like the game is really confused and has maybe corrupted your savegame. Try using Chapter Select (the [C] key, or available in the pause menu) to rewind to the latest unlocked chapter. You'll lose a bit of progress and all your gossips will need to be replayed, but it should reset the game to an uncorrupted state.
I'll keep looking for fixes! Thanks for letting us know about the bugs! <3