Exactly what rights you have are impossible to say without much more information. You could own the land at the bottom of the pond (the "solum") to wherever your property extends. You (or a previous owner of your property) might have ceded ownership or some of your rights over that solum when the dam was built that created the pond. You probably have the right to access the water in the pond and may have riparian rights to the use of it. Any of these rights might be modified by statute as well. So without knowing a whole lot more about your situation, it's tough to say.
What's riding on this?