23 VORTEX. This vortex of fresh water deposits those traveling from Room 30 of the Upper Dungeons Level 3 into the Salt Mere. Traveling this route does 4d4 damage of crushing and smothering. Those who can water breathe suffer only 2d4 damage.
From Level 3A, the vortex appears as a intimidating column of rushing water. Approaching it by swimming and getting dragged into it will cause damage as above. It is strong enough to capsize boats.