I have shot over rice paddies with lead, over an old fish farm pond with lead (a few weeks ago) and other scenarios. Some have, by now, been halted; others it seems would depend on whether the water can be contained (like a pond), whether there are Federally controlled migratory birds, and on and on. Wisconsin F&G might be a good place to start - start low and locally and work your way up the Feds and the EPA