WATER VULNERABILITY
Types: Flaw, Innate, Tier 1.
Prerequisites: Construct, Outsider, or Undead; cannot be aquatic.
Benefits: You don't breathe but you treat running water and being totally submerged as lethal using the same rules as drowning for a living creature. If you take this a second time, you must choose Rust or Acid. If you choose Rust, you're afflicted with Rust every time you're submerged or partially submerged in water. If you take a third time you're afflicted with Rust even when only partially submerged. If you choose Acid, you treat running water like acid, taking damage from it (10d6 if submerged, 3d6 if partial, 1 if splashed). Still water deals half damage. If you take this a thid time, this damage increases to (20d6 if submerged, 5d6 partial, 1d6 splash).

Rust
Fortitude DC (30 if submerged, 20 partial, 10 splashed)
1d6 Dex damage and 1 Strength damage per day, petrified if reduced to 0 Dex or Str by this effect
1 save ends