Stealth Umi Control

The goal of this deck is to play a controlling tempo game. There are an absolute mess of synergies in this list, and I don't think I've found them all.

Essentially, you want to get an Umi floodgate package online using the Ocean Dragon Lord, then follow up with removal in the form of Virtue Stream. But don't think this is just an Umi deck. Sea Stealth Attack does so much work, especially alongside Sea Stealth II. Attack allows you to flicker your own monsters, which, in tandem with Sea Stealth II, allows you to bring a summon from your graveyard to the battlefield, then banish it so that it stays on your battlefield permanently starting at the end of the turn. This allows you to aggressively re-use your summons as xyz summon material for bahamut shark, which will get leVirtue Dragon.

You can also use Doom Kraken and Sea Stealth Attack to remove the summon you target with virtue stream, allowing you to destroy 2 permanents your opponent controls while not losing material yourself.

Because of the pressure that your back row generates, your opponent will feel the need to address it, and that's where waking the dragon and trap trick come into play. They will allow you to cheat a raidraptor into play, or a citadel whale or a floodgate from your deck, if you need one. LeVirtue Dragon can also move material to raidraptor every turn from other xyz, if necessary, which will allow you to actually use it's ability as well.

Lastly, Foolish Burial Goods and Ice Barrier really tie the entire deck together, allowing you to more consistently get to a board state with Umi on the battlefield and other floodgates. Fury of Kairyu-Shin is another great burial goods target, as it will force your opponent to find an additional destroy effect to escape your locks. 

Mixing Sea Stealth Attack and a traditional Umi strategy with a small, tight package of sharks allows you to utilize an extra deck to cover weaknesses in your strategy, and give you more flexibility in how you approach any given board state. Good Luck out there!