and it's creatures!!!!!!
MONSTERS: [21]
[02x] Abyss Soldier
[01x] Atlantean Attack Squad
[03x] Atlantean Dragoons
[03x] Atlantean Heavy Infantry
[03x] Atlantean Marksman
[03x] Deep Sea Diva
[01x] Genex Ally Birdman
[02x] Genex Controller
[03x] Genex Undine
SPELLS: [10]
[01x] Allure of Darkness
[01x] Dark Hole
[01x] Heavy Storm
[01x] Mind Control
[01x] Monster Reborn
[02x] Mystical Space Typhoon
[01x] Pot of Avarice
[02x] Salvage
TRAPS: [09]
[02x] Bottomless Trap Hole
[02x] Dimensional Prison
[01x] Solemn Judgment
[02x] Solemn Warning
[02x] Torrential Tribute
EXTRA DECK: [15]
[01x] Ally of Justice Catastor
[01x] Armory Arm
[01x] Black Rose Dragon
[01x] Dewloren, Tiger King of the Ice Barrier
[01x] Gaia Knight, the Force of Earth
[01x] Gungnir, Dragon of the Ice Barrier
[01x] Scrap Dragon
[01x] Stardust Dragon
[01x] Daigusto Phoenix
[01x] Gachi Gachi Gantetsu
[01x] Leviair the Sea Dragon
[01x] Number 17: Leviathan Dragon
[01x] Number 30: Acid Golem of Destruction
[01x] Temtempo the Percussion Djinn
[01x] Wind-Up Zenmaines
The focus of this archetype is to swarm the field with Level 3 or lower WATER monsters with the effects of "Atlantean Marksman", "Deep Sea Diva" and "Atlantean Heavy Infantry" to later Tribute them for the summon of their ace monster, "Poseidra, the Atlantean Dragon", or to Synchro Summon with "Deep Sea Diva" and "Genex Controller", preferably the "Ice Barrier" Synchro Monsters.
Also, the effects of "Atlantean Marksman", "Atlantean Heavy Infantry" and "Atlantean Dragoons" trigger when they are sent to the Graveyard as cost for a WATER monster's effect, so cards like "Abyss Soldier" and "Gungnir, Dragon of the Ice Barrier" would be a good add to the Deck.
Interestingly, the Atlantean effects also activate if they are detached from an Xyz Monster (the effect only requires the monster to be sent to the Graveyard, like "Dandylion"), so a great addition to this deck are WATER Xyz Monsters, like "Number 17: Leviathan Dragon". Here is a list of WATER Xyz Monsters that can Trigger the Atlantean's effects (note that all current Atlantean that share this effect are Level 2, 3 or 4.
Here's a link to some of the decks plays and combos.