Who Owns The Water?

Australia and Canada...

It is mostly the same in the USA. Thing is you will likely get a safety check if you get the harbor police called out by pesky marina and property owners on the shore, so make sure you have that stuff in order if you stand your ground.

Be respectful and professional: Everyone has cameras.

It gets way more complicated with riparian rights. Generally navigable waters are open to boat traffic and property owners on the sides cannot prevent you from using the river. Dams and impoundments, however, have different issues (such as restrictions for Homeland Security). There are some states that allow ownership of tidelands.