I looked through all the tags on the wiki, but I can't really see anything good enough. I don't personally know of any other location that is already tagged, so I can't find any examples either. It's very much possible such tags don't exist (yet).

If I had to tag the activity, I would probably follow `attraction=bumper_car` method and use `attraction=bumper_boat` . Here is an example https://www.openstreetmap.org/node/9906555477 . But this might imply a more "aggressive" activity, so I don't know. Something more established like `attraction=boat_ride` seems too big for this.

The water I would map as a pond.