I know games like SM64 had this conept before, but i remember experiencing this in Jak and daxter for the first time.

IM talking abotu when you try and swim out to see and the big fish eats you. I liked how they didnt place an invisible barrier there and they implemented like something that tied into the game. And I also liked how in GTAs when you swim out the body of water extends out infinitely.
I just thought it was interesting and even though their essentially replacing the wall with something else that limits your movements I thought it was a step forward.

I don't know why people have a thing against invisible walls.  They're there to protect you.

I think the GTA games have walls, you get have to go out in the water reallly far and you will find it. I`m not sure about Gta:4 though, don`t cops just shoot you up if you go out to far in that one or something.

WEll I remember in San Andreas I swam to the top of the map and I kept swimming and I just got further and further away.

I did the same thing in GTA IV with a helicopter.