Homosassa River, Where does fresh water start and ocean end?

[FreedivingFilms]

If you go to the Weeki Wachee River in Hernando County, I spoke to the game warden and he said the ocean starts at the bridge near the Upper Deck bar at Rogers Park. West of the bridge is considered the ocean and you can spear fish; east of the bridge you can't spearfish. It's illegal.
Does anybody know what the same situation is for Homosassa River??? This info is not written in the fishing regs. Thanks! FreedivingFilms