Text (VI+errata): 4/4, Flying. ; At the beginning of your upkeep, sacrifice ~this~ unless you return an untapped Island you control to its owner's hand. [Oracle 2003/07/01]
You choose a land to return and return it during resolution of the upkeep triggered ability. This means if you have two Waterspout Djinns, they must each return different Islands. [D'Angelo 1999/07/10]