Your hull integrity shouldn't have been at 11% already. A conflicting mod maybe?
If you're taking damage without actually being attacked I'd say there's a big problem. You may want to check the subs .zon file. Make sure those hitpoints are higher. And the armor is set to 5 or close to that.
FYI Though. If you set all the flotability areas except the rooms you'll be invincible on the surface. I at least suggest you set the fuel tanks back to 100+.