Rockstar says there will be five times as many pedestrians in GTAV as there were in Grand Theft Auto IV
There's a "crazy level of detail": Tourist buses can be boarded for a tour of celebrity homes, film posters are plastered on the walls, men in comedy costumes try to corner you outside the Cathay Theatre, including the Superman-like Impotent Rage and Master Chief riff, Space Ranger.
The geographical scope is huge and spans:
Dense urban environments...and more
An underwater ecosystem exits, "the sea is teaming with fish and sharks"
A deer and a wildcat were spotted in the mountains.
Some more stuff LINK