Splash Attack

[Toffee.]

you can unlimit this and the baby then ban every other ruler and WATER still won't be good

So....

Reveal 1 WATER monster in your hand to your Opponent, then return it to the bottom of your Deck. Then, you can take 1 Level 1 WATER monster from your Deck, and either add it to your hand or Special Summon it in either face-up Attack Position or Face-down Defense Position. You can only activate 1 Splash Attack per turn. You cannot Special Summon monsters for the rest of this turn, except WATER monsters.

Best target is clearly Neptabyss, guise.
This can also play Treeborn Frog, Beautuna, Mermaid Shark, Puny Penguin, Ghost Fog, etc, etc, all the cool stuff that WATER has.