>>337966887
The map in the link here >>337879484
has the swimming system already installed but you will have to open the swimming mechanic inside the building nearby and activate the fbt mode.

As for the three-legged race, anon managed to create a proper working one recently up for a bit more udon testing but it's pretty cool how each of your partner's foot needs to be inside the big red cylinder for it to be moved.
So you'll really have to work together.
See webm related