Umi Control Deck Breakdown
Main Deck
Electric Jellyfish
ATK:
1400
DEF:
1700
You can send 1 "Umi" from your hand, Deck, or face-up field to the GY; Special Summon 1 WATER monster from your hand. When your opponent activates a monster effect, or Spell Card or effect, while "Umi" is on the field (Quick Effect): You can negate that effect, then, you can make this card gain 600 ATK/DEF. You can only use each effect of "Electric Jellyfish" once per turn.
Mega Fortress Whale
ATK:
2550
DEF:
2350
If "Umi" is on the field: You can activate this effect; your WATER monsters can attack directly this turn. During your opponent's Battle Phase (Quick Effect): You can target 1 face-up monster your opponent controls; destroy it. If this card on the field is destroyed by battle or card effect: You can either add to your hand or Special Summon 1 WATER Warrior monster from your Deck or GY. You can only use each effect of "Mega Fortress Whale" once per turn.
Ocean Dragon Lord - Kairyu-Shin
ATK:
2000
DEF:
1700
While "Umi" is on the field, each player can only control 1 face-up non-WATER monster. (If a player controls 2 or more, they must send some to the GY so they only control 1.) During your Main Phase: You can add from your Deck to your hand 1 "Umi", 1 "Kairyu-Shin" Spell/Trap, or 1 "Sea Stealth" Spell/Trap. You can only use this effect of "Ocean Dragon Lord - Kairyu-Shin" once per turn.
Sea Stealth II
This card's name becomes "Umi" while on the field or in the GY. Your opponent cannot target WATER monsters you control with non-WATER monster effects. At the start of the Battle Phase: You can Special Summon from your hand or GY, 1 monster that mentions "Umi", or 1 WATER Normal Monster, in Defense Position, but destroy it at the end of the Battle Phase. You can only use this effect of "Sea Stealth II" once per turn.
Sea Stealth Attack
When this card is activated: You can activate 1 "Umi" from your hand or GY. While "Umi" is on the field, this face-up card gains these effects. ● Once per turn: You can banish 1 WATER monster you control until the End Phase; this turn, face-up Spells/Traps you control cannot be destroyed by your opponent's card effects (even if this card leaves the field). ● At the start of the Damage Step, if your WATER monster whose original Level is 5 or higher battles an opponent's monster: Destroy that opponent's monster.
Main: 40
Electric Jellyfish
ATK:
1400
DEF:
1700
You can send 1 "Umi" from your hand, Deck, or face-up field to the GY; Special Summon 1 WATER monster from your hand. When your opponent activates a monster effect, or Spell Card or effect, while "Umi" is on the field (Quick Effect): You can negate that effect, then, you can make this card gain 600 ATK/DEF. You can only use each effect of "Electric Jellyfish" once per turn.
Gameciel, the Sea Turtle Kaiju
ATK:
2200
DEF:
3000
You can Special Summon this card (from your hand) to your opponent's field in Attack Position, by Tributing 1 monster they control. If your opponent controls a "Kaiju" monster, you can Special Summon this card (from your hand) in Attack Position. You can only control 1 "Kaiju" monster. When your opponent activates a card or effect, except "Gameciel, the Sea Turtle Kaiju" (Quick Effect): You can remove 2 Kaiju Counters from anywhere on the field; negate the activation, and if you do, banish that card.
Mega Fortress Whale
ATK:
2550
DEF:
2350
If "Umi" is on the field: You can activate this effect; your WATER monsters can attack directly this turn. During your opponent's Battle Phase (Quick Effect): You can target 1 face-up monster your opponent controls; destroy it. If this card on the field is destroyed by battle or card effect: You can either add to your hand or Special Summon 1 WATER Warrior monster from your Deck or GY. You can only use each effect of "Mega Fortress Whale" once per turn.
Ocean Dragon Lord - Kairyu-Shin
ATK:
2000
DEF:
1700
While "Umi" is on the field, each player can only control 1 face-up non-WATER monster. (If a player controls 2 or more, they must send some to the GY so they only control 1.) During your Main Phase: You can add from your Deck to your hand 1 "Umi", 1 "Kairyu-Shin" Spell/Trap, or 1 "Sea Stealth" Spell/Trap. You can only use this effect of "Ocean Dragon Lord - Kairyu-Shin" once per turn.
Anchamoufrite
ATK:
1800
DEF:
0
[ Pendulum Effect ] If you have no cards in your Extra Deck except "Anchamoufrite": You can destroy this card, then draw 1 card. You can only use this effect of "Anchamoufrite" once per turn. [ Monster Effect ] Cannot be Normal Summoned/Set. Must be Special Summoned (from your face-up Extra Deck) by having no cards in your Extra Deck except "Anchamoufrite". You can only Special Summon "Anchamoufrite" once per turn this way. If this face-up card in the Monster Zone leaves the field, banish it.
Sea Stealth II
This card's name becomes "Umi" while on the field or in the GY. Your opponent cannot target WATER monsters you control with non-WATER monster effects. At the start of the Battle Phase: You can Special Summon from your hand or GY, 1 monster that mentions "Umi", or 1 WATER Normal Monster, in Defense Position, but destroy it at the end of the Battle Phase. You can only use this effect of "Sea Stealth II" once per turn.
Small World
Reveal 1 monster in your hand, choose 1 monster from your Deck that has exactly 1 of the same Type, Attribute, Level, ATK or DEF, and banish the revealed monster from your hand face-down. Then add, from the Deck to your hand, 1 monster that has exactly 1 of the same Type, Attribute, Level, ATK or DEF as the monster chosen from your Deck, and banish the card chosen from the Deck face-down. You can only activate 1 "Small World" per turn.
Triple Tactics Thrust
If your opponent has activated a monster effect during this turn: Set 1 Normal Spell/Trap directly from your Deck, except "Triple Tactics Thrust", or if your opponent controls a monster, you can add it to your hand instead. That Set card cannot be activated this turn. You can only activate 1 "Triple Tactics Thrust" per turn.
Infinite Impermanence
Target 1 face-up monster your opponent controls; negate its effects (until the end of this turn), then, if this card was Set before activation and is on the field at resolution, for the rest of this turn all other Spell/Trap effects in this column are negated. If you control no cards, you can activate this card from your hand.
Kairyu-Shin's Dark Reef
Send 1 face-up "Umi" you control to the GY; Special Summon up to 2 monsters with different names from your hand and/or Deck, that mention "Umi" or are WATER Normal Monsters, in Defense Position, then if your opponent controls a monster, you can Special Summon any number of Level 6 or lower WATER Normal Monsters from your hand and/or Deck. Until the end of your next turn after this card resolves, you cannot Special Summon monsters, except WATER monsters. You can only activate 1 "Kairyu-Shin's Dark Reef" per turn.
Sea Stealth Attack
When this card is activated: You can activate 1 "Umi" from your hand or GY. While "Umi" is on the field, this face-up card gains these effects. ● Once per turn: You can banish 1 WATER monster you control until the End Phase; this turn, face-up Spells/Traps you control cannot be destroyed by your opponent's card effects (even if this card leaves the field). ● At the start of the Damage Step, if your WATER monster whose original Level is 5 or higher battles an opponent's monster: Destroy that opponent's monster.
Trap Trick
Banish 1 Normal Trap from your Deck, except "Trap Trick", and Set 1 card with the same name directly from your Deck, also it can be activated this turn. You can only activate 1 Trap Card for the rest of this turn after this card resolves. You can only activate 1 "Trap Trick" per turn.