I would keep route=swimming, it sounds like an interesting concept.

Here are the tags I would remove from both ways:

ford=yes (it's not a path crossing a watercourse)

highway=path (it's not a path)

incline=0% (water stays flat by default)

location=underwater (folks are not forced to dive, I guess)

smoothness=impassable (not relevant since this is not a path)

surface=water (I hope the whole thing is water, not just the surface :-) )

trail_visibility=no (Again, not a path)