Pools are bodies of water. The Lord directed Isaiah to meet Ahaz with Shearjashub “at the end of the conduit of the upper pool in the highway of the fuller’s field” (2 Nephi 17:3).
The Lord of Hosts said, “I will also make it a possession for the bittern, and pools of water”. He also said, “I will sweep it with the besom of destruction” (2 Nephi 24:23).