>>43476518Right, the centre of the lake is the former magna chamber which has collapsed connecting it to the sea. Before the collapse of had filled with fresh water which is lighter than salt water. Since fresh water is lighter than sea water it "floats" onto of the sea water. This is why you can catch different pokemon inside and outside.
As for the cave that is an old magma tube that leads down into a fresher magma chamber(ruby) or a flooded magma chamber(sapphire)
Why do people live there? People live near stuff that looks cool for only that reason.
