Umi Synchro

Sometimes Konami prints 1 card that makes a deck that was otherwise unviable just work. That card was General of Atlantis, as it is able to not just get Umi but also put a free body on board.

The one-card combo (+2 discards) for this deck is First Penguin, and it ends on a WATER Synchro of your choice (normally Dragite), Ocean Dragon Lord - Kairyu-Shin, Kairyu-Shin's Dark Reef to either protect kairyu-shin or to summon Electric Jellyfish, and an effective Forceful Sentry because of Magellanica itself. This is also achieved by having Revealer of the Ice Barrier + a way to Magellanica.
The combo is as follows:
1. Summon Penguin, discard and reveal Brionnac to add General.
2. Discard General to add Advent.
3. Activate Advent, then summon General from GY.
4. Use the effect of Advent to place Magellanica from your Deck.
5. Use Magellanica to increase the level of either Penguin or General by 1.
6. Synchro for Prima Donna, using Magellancia to look at our opponent's hand and rip a card from it.
7. Use Prima Donna to return the ripped card and summon Revealer from the Deck.
8. Use Revealer to discard and summon Mirror Mage from the Deck. 
9. Synchro for Dewloren, using Mirror Mage to add Freezing Chains to your hand.
10. Activate Freezing Chains, reborning Mirror Mage.
11. Use Dewloren to bounce the Magellanica and Freezing Chains.
12. Activate Magellanica, placing Kairyu-Shin on top of your Deck.
13. Use Mirror Mage, tributing Dewloren to summon 3 tokens and increase its level by 3.
14. Use Magellanica to increase Mirror Mage's level by 2.
15. Synchro for Crocodragon using Mirror Mage and 2 Levels tokens, having CL1 being Croc to draw 2 cards, one of which will be Kairyu-Shinl, and CL2 being Magellanica to rip a card from your opponent's hand.
16. Synchro for Dragite using the final token and Prima Donna, using Prima Donna to shuffle the ripped card into the Deck.
17. Tribute Summon Kairyu-Shin using Crocodragon, using Kairyu-Shin to add and then set Dark Reef.
18. On your opponent's turn, if you know they don't have anything like Ash or Dark Ruler, activate Dark Reef, sending Magellanica to summon an Electric Jellyfish and a second Kairyu-Shin from your Deck.

How to Play Around/Into Handtraps:
- Fuwalos: Tribute Summon Kairyu-Shin (and if you like, first synchro for Prima Donna so you get hand knowledge and rip a card out the opponent's hand by tributing over it)
- Purulia or Meowls: Do the combo and give them the 2 draws (Purulia:  penguin and kairyu-shin | Meowls: General and Mirror Mage)
- Nibiru: Summon Jellyfish off Prima Donna as your fifth summon, then summon kairyu-shin if possible
- Shifter: Tribute Summon Kairyu-Shin if possible (harder because goods and electric jellyfish are no longer live)
- Droll: Cry in a corner, unless you have access to Kairyu-shin and Umi, in which case you tribute summon Kairyu-Shin. (NOTE: Goods is live under Droll)
- one for one handtraps (ash, imperm, impulse): this deck can't easily play around them, but if you have revealer, or any umi card then you can either make kairyu-shin or do full combo still.

Going Second:
Use Kairyu-shin / A Legendary Ocean as threats to wipe the opponent's board, use Ice Barriers as way to combo and partially wipe boards, Thrust can essentially get you to any card you need, If not locked into waters you should make Ty-Phon after Kairy-shin (likely on top of General) and bounce the opponent's last monster. THIS DECK CANNOT EASILY OTK, but it slows the game down to a point where you will kill them in 2 turns.
- for specific match-ups, side in Gameceil and/or Medium as additional targets to search off Goods.

WATER match-up (harder as kairyu-shin is way less powerful):
- Generally: side in Arms to make Reef two negates instead of 1, and side in Lancea and Georgius (for Prima Donna and Freezing Chains respectively) to increase the combo potential (and thus power) of your end board.
- Xyz and Synchro Decks (shark, goti, etc.): use A Legendary Ocean to mess levels up for them, and back it up with WATER Synchro's and Jellyfish/Arms.
- Link and other Decks (Atlantean, Marincess, etc.): Rely more on Lancea / Gergious as a way to box out the GY. 

Backrow Match-up:
- Use Medium of the Ice Barrier as your Floodgate of choice. This is also searchable/Summonable off Magellanca and Lancea going first, and goods (and thus Ice Barrier) going second. Use Aegirine to make board sticky and hard to remove.