The No-name community is the only community shown possessing a water tree, won by Izayoi Sakamaki from a gift game with a water god in Episode 1 - The Problem Children Have Arrived at Hakoniwa, Haven't They?. Black Rabbit comments on how theirs is a "large" water tree sapling.
News of its whereabouts after the anime
Small branches were trimmmed from the water tree and stored within Gift cards for use during combat as water rations. Main tree remains at Community. A super large version of it, the parent, is at the Southern territories named as UnderWood Great Tree.