From what i've read, the navigable vs non-navigable argument is only relevant to deciding ownership of the land beneath the water (i.e. mineral rights) and has nothing to do with the scenario in the original post. As far as i can tell, any body of water with sufficient size & depth to float a "pleasure" boat is available for public use regardless of who owns the land below. So if that body of water is accessible through a public domain, such as an easement, then there should be no issues with recreational use.
Of course, that won't stop the adjacent land owners from trying to restrict access and convince law enforcement to issue trespass summons; but i'm pretty confident the courts would side with public use. It just depends on how much you want to wrestle with the red tape.
There was a similar situation near where i grew up. A large lake surrounded by private land with no public access. Eventually the water rose enough that it butted up against a township road. People started driving out on it to ice fish, which enraged the nearby landowner. He convinced the sheriffs to ticket the people, but when taken before a judge were all dismissed. In the end, the only thing the landowner was able to do was convince the township to put no parking signs along that stretch of road.
Of course, that won't stop the adjacent land owners from trying to restrict access and convince law enforcement to issue trespass summons; but i'm pretty confident the courts would side with public use. It just depends on how much you want to wrestle with the red tape.
There was a similar situation near where i grew up. A large lake surrounded by private land with no public access. Eventually the water rose enough that it butted up against a township road. People started driving out on it to ice fish, which enraged the nearby landowner. He convinced the sheriffs to ticket the people, but when taken before a judge were all dismissed. In the end, the only thing the landowner was able to do was convince the township to put no parking signs along that stretch of road.