Number 47: Nightmare Shark

YZ04-JP001 
No. 47: Nightmare Shark 「Ｎｏ．４７ ナイトメア・シャーク」
WATER/Sea-Serpent - Xyz - Effect/Rank 3/2000/2000
2 x Level 3 Monster
If this card is successfully Special Summoned, you can select 1 Level 3 WATER Monster from your hand or that you control and place it as Xyz Material under this card. Once per turn, you can activate this effect by removing 1 Xyz Material from this card and select 1 WATER Monster you control. During this turn, other Monster than the selected Monster cannot attack, and the selected Monster can attack your opponent directly.

You could make this pretty easily in Merlantean, it activates their effects, but I don't see anything spectacular about it in particular. Bahamut does summon this AND you can put a material under it when it is Special Summoned, so it may turn out well. Only time and results will tell.