Wanton destruction is half the fun of playing Grand Theft Auto, which can mean everything from picking a high point on a building with a sniper rifle and a bag of pop-corn, to rolling down the highway in a tank, blowing up everyone that tries to stop you. However that's child's play compared to what damage can be done when you introduce mods like the Tsunami one, which literally covers the world and turns Los Santos into Kevin Costner's back yard.
Fortunately for our protagonist in the latest GTA, helicopters are available for him to get about in, so he doesn't have to resort to wind or "smoker," oil, but there is a whole lot less to look at once everything has been covered by water.
Some of the higher hills survive, along with the homes located on them, but everything else is totally covered when the mod is installed. But that doesn't mean you can't go down there, or in-fact, that the world has changed all that much.
If you swim down, you might be able to find the ghosts of vehicles still driving the submerged streets, and funnily enough, people walking the pavements too. Until you swim close enough that is and physics becomes enabled.
Our advice for surviving the water-world GTA? Make sure you have some paper to trade.