Flooding Room CR 8
Source: Pathfinder Adventure Path #34
The room is completely flooded in 10 rounds, at which point the entrances slam shut. Objects or creatures in doorways when this occurs take 8d6 points of damage—a DC 15 Reflex save allows a creature or attended object to avoid the damage but only if it immediately shifts out of the doorway to one side or the other.
Trigger touch; Onset Delay 1 round; Reset none
Effect rushing water (targets directly in areas of rushing water are knocked prone and take 2d6 bludgeoning per round; DC 20 Reflex avoids); room fills completely with water in 10 rounds (water increases in depth by 1 foot every round)