1 Earth Elemental: Halt, intruders.
1 Dwalin: An earth elemental!
2 Lambert: Mordekai, you're supposed to be scouting. Why didn't you warn us about this?
3 Mordekai: It's just a pile of rocks! What's to warn about?
4 Mordekai: Sheesh! What else do you want me to warn you about? Pools of water? Doors? Stalactites? Pit traps? Dragons??

Of course any Dungeons & Dragons player worth their salt will know that all of those items are dangerous.

Especially the pools of water.

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2025-03-18 Rerun commentary: Pools of water feature in the very first published Basic Dungeons & Dragons adventure: B1 In Search of the Unknown. Room 31 of the dungeon is the infamous "Room of Pools", described as follows:

Arrayed throughout the room are fourteen different pools, each about ten feet in diameter, with sides sloping to a maximum depth of five feet in the center. This mystical arrangement is doubly amazing, since all the contents of the pools are different. . .

Some of the pools are full of more or less normal, harmless water. But others are full of... other things. It appears that the intention is that curious players will have their characters try drinking or tasting some of the pool contents, or perhaps experimenting with them in other ways. Some of them could indeed be useful or beneficial, but honestly the entire room is just best avoided!

It is great fun, though.