[Terquem]

I've used a fast flowing, but shallow, and slippery, watercourse in a cavern before. With Dex rolls to cross and failure means the individual is swept away (I allow bonuses to the rolls for characters that rope themselves together, but failure here means the whole group can get swept away)

Sometimes the party ends up getting swept to a different location in the dungeon, dumped in an underground lake, or swept out of the dungeon to the wilderness.