How to Build a Yu Gi Oh! Water Deck

Buy a SD4 (Structure deck 4 Fury From The Deep). It has most of the cards you need for a water deck; for example, Levia-Dragon Daedalus

From your Starter deck, it is highly recommended you use all 3 of your Mother Grizzly and A Legendary Ocean. You can use your Levia-Dragon - Daedalus, Codarus, or both(Codarus is a card upcoming in Absolute Powerforce). At least 1 is recommended. Depending on the number of the above 2 cards you include, add in some Forgotten Temple of the Deep, also in Absolute Powerforce. This will count as "Umi" for Daedalus' and Codarus' effects.

Find cards that will boost any WATER deck such as Warrior of Atlantis, a versatile card you could use to search out "A legendary Ocean", and Aqua Spirit, a Special Summon monster with decent ATK and a good Control Effect. The number of Aqua Spirit(s) should vary depending on your type of water deck, but you should always have 3 Warrior of Atlantis. WATER decks can be used in all 3 general deck strategies: Beatdown, Control or Combo. Choose what type your WATER deck will be.

If you choose Beatdown, get some High ATK Level 5 WATER monsters like Giga Gagagigo and Terrorking Salmon, which can be summoned without tribute from A Legendary Ocean. Use High ATK level 4 WATER monsters as well like Gemini Lancer, Abyss Soldier and Blizzard Dragon, although it has a Control Effect it still has High ATK. It's OK and actually encouraged for your Beatdown Deck to have a few Control elements and vice versa. Add in 1 or 2 Amphibious Bugroth MK-3, Mermaid Knight, and Star Boy. Use Spell cards that will help with Attacking or Swarming like Big Wave Small Wave or Hydro-Pressure Cannon (which will work with Level 4s from A Legendary Ocean). Generic Destruction Trap cards like Mirror Force and Sakuretsu Armor are recommended.

If you choose Control, get cards like Gora Turtle, Maryokutai, B.E.S. Crystal Core, Nightmare Penguin and Penguin Soldier, which will all help you control the field and remove opponent's monsters. Add in 1 or 2 Amphibious Bugroth MK-3, Mermaid Knight, and Star Boy, although this deck will have less of these monsters than the Beatdown deck. Since most of these cards will be Low Level and Low Attack, use at least 2 Salvage, 2 Aegis of the Ocean Dragon Lord, and 1 Hydro Pressure Cannon. Use Gravity Bind and/or Level Limit Area B which is a must for Control Decks. Keep in mind Level Limit is Limited and Gravity Bind is Semi-Limited.

If you choose Combo, this means that you heavily rely on Levia-Dragon - Daedalus' and Codarus' Effects. In this deck, use a high number of either or both of them. If you have mostly Codarus' in your deck, then you want Low-Level Support Cards like Salvage and Mother Grizzly to search it out. If you have mostly Levia Dragon, use Big Wave Small Wave to summon it easier and Aegis of the Ocean Dragon Lord to protect your weaker monsters from his effect. And if you have AT LEAST 2 Levia-Dragon - Daedalus, add in an Ocean Dragon Lord - Neo-Daedalus, NO MORE than 2 because he is a "dead draw". Use 3 Forgotten Temple of the Deep, and 1 or 2 Pseudo Space to copy A Legendary Ocean.

Even if you only plan to use a Beatdown or Control-centered deck, read steps #5 - 7 to get more ideas for your deck. WATER decks are very versatile in this way and can change their playing style to fit the situation.

It can be a good idea to collect "Shark" cards from the new show. Shark uses a variety of strong level 3 monsters to Xyz summon. Rank 3 monsters are currently the most populated, with 7, so you have plenty of options! However, the only two water Xyz monsters are Submersible Carrier Aero Shark and Leviathan Dragon.