Cars in tunnels float up

[JayFoxRox]

I've been able to reproduce an issue which has been mentioned before (but not documented here?!):

If you spawn vehicles in a tunnel (but not all of the tunnels?) they float up (because they are underwater probably). Interestingly, this does not happen to cars which you drive into the tunnel (Banshee on the right).

When I tried to reproduce this last time, I only got some vehicles to float up, but I couldn't repeat it elsewhere and was unable to drive to those points as I forgot where I spawned the floating cars. I drove through the tunnels searching for them but had no luck floating up or finding my cars (and I've tried various spots underwater and under land!)

[Lihis]

Tested against b7fb22f.

Spawned cars still float for example in metro tunnel, confirmed at least this section marked in red:

Also the beginning of the tunnel from airport towards second island might be affected. Needs to be confirmed as my game started to crash randomly in airport area.

[Lihis]

The tunnel which entrance is near Stadium in Staunton Island:

AI driven cars, which spawn from this point, until the intersection where you can go either Portland Island or Shoreside Vale will float up:

Also happening at parts of this tunnel which lead to airport. AI driven cars seems to only float up only if they spawned at affected area, if they drove to affected area they don't float up.