Text (FE+errata): Until end of turn, whenever a player taps an Island for mana, that player adds {U} to his or her mana pool (in addition to the mana the land produces). [Oracle 2009/02/01]
Multilands which are part Island produce an extra blue mana in addition to whatever you tap it for. [Aahz 1994/12/03]
Non-lands or lands which do not say they count as Islands do not produce extra mana. [Duelist Magazine #4, Page 6]
It affects lands you control when it resolves and any lands you gain control of this turn. [D'Angelo 1999/10/05]
Extended tournaments (see Rule 913) have banned this card since 1999/10/01.
