I'm sure if the boats are packed, they might check, but it's never happened to me. If they do check, just walk over or tell the boat driver you want to visit the restaurants. I've visited the hotels when not staying onsite.
One time I went to the HRH to get the current bus schedule to SWF, tuff work but someone had to do it. I went in thru the pool and grabbed a Heinekin draft at the bar. Then I crashed on a lounge chair and a waitress asked if I wanted another beer. Ok, don't twist my arm. I had a couple beers before walking back to the parks.
If a bunch of people showed up and tried to ride over on the boat and use the pool, they'd be a little peeved. This doesn't happen often because it doesn't "feel" like you're supposed to be there, unless you have an upcoming visit, or have been there recently. The flip side to this, is they'd want people visiting the restaurants whether they are staying onsite or not.