Getting a boat onto the wheels in the water can be a chore
I just push my cat out into slightly deeper water and slide the wheels under without any problem
I normally do mine in deeper water as well. In some situation we use 2-3 people per boat, so I can see the desire for a less buoyant wheel system. If going up and down a boat ramp is the norm, I would suggest the narrower wheelbarrow style wheels seen on A class dollies.
