What's after the invisible wall in the sea of GTA San Andreas?

I'm sure that there's no Liberty City in that game, because it'd be a terrible waste of time and the concept of liberty city wasnt even out when san andreas was being made....there's nothing past that wall. its just an invisible barrier with some colors in the background to make it seem like it goes further. i dont even know if you're trolling or not, but if you are, well done sir