Oceanic Conversion, Atlantis Dolphin

-Opponent Turn's Guard Step-[Choose a card with "[Heal] Heal" from your hand, and discard it] Call this card to your from face down. :When placed on during the battle that your opponent's vanguard attacked, [choose a face down from your G zone, and turn it face up], and this unit gets +5000 until end of that battle for each of your rear-guards. If this unit's is 30000 or greater, 1/ 1.