More Water

[Ryusei the Morning Star]

Leviathan no Ikari / Rage of Kairyun-Shin
Quick-Play Spell Card
You can only activate 1 card with this card’s name per turn.
(1) If “Umi” is on the field: Target a number of monsters your opponent controls, up to the number of WATER monsters you control whose original Level is 5 or higher; destroy as many of them as possible, and if you do, those Monster Zones cannot be used until the end of next turn.

 

Sea Stealth Attack
Continuous Trap Card
(1) When this card is activated: You can activate 1 “Umi” from your hand or Graveyard.
(2) If “Umi” is face-up, this card gains these effects.
• Once per turn: You can banish 1 WATER monster you control until the End Phase; during this turn, face-up Spell/Trap Cards you control cannot be destroyed by your opponent’s card effects.
• At the start of the Damage Step, if a WATER monster you control whose original Level is (5?/6?) or higher battles an opponent’s monster: Destroy that opponent’s monster.

[Premier Alexander Romanov]

Rage is great in this Link-centric format, as you can just lock down your opponent's Linked Zones (I think that's the proper terminology) and set them back big time.
Sea Stealth Attack is pretty good, but even better considering Stronghold Whale gets this card out upon Summon. It supports both the banishing that WATER monsters became so obsessed with for a time and works with the big WATER monsters, too by giving them a Catastor effect.

[Atypical-Abbie]

Rage of Kairyun-Shin, not bad, I'm a fan of Umi, so that's fun, Phantasmagoric Dragon could potentially use it. Locking down the Extra Monster Zone is going to be useful as well.

 

Sea Stealth Attack, searchable by the Stronghold Whale, being able to bring back a Umi from the Graveyard is interesting I suppose, a semi-Catastor effect is good too, being able quickly get out of the way of an opponent's card effect and protect your backrow is neat too.

[Tinkerer]

Sea Stealth Attack can also protect Equip Spells for that Normal Monster supporting Umi

[Krashkube]

They released a spell based around Kairyushin before they printed the man himself in the TCG, wow

 

Locking down the extra zones and link zones can set the opponent back by a ton too although you do need Umi and some l5 or higher waters out.

[Neutrality Man]

This trap also resets Non-Link Extra WATER monsters to the Main Zone.