Merlantean

The Genex Atlantean Mermail Deck, also known as G.A.M. and Genex Sea Emperor Mermail, is a deck that uses the destruction and searching effects of the Atlantean monsters with the discarding costs of the Mermail monsters to clear the opponent's field while also maintaining field presence and hand advantage.

The Genex monster "Genex Undine" is a versatile monster that can send any WATER monster from the deck to the Graveyard as a cost to add "Genex Controller" to your hand, being able to use any of the Atlantean effects directly from the deck. With "Genex Controller" in your hand, running "Allure of Darkness" is also an option.

"Atlantean" monsters have their effects triggered when they're sent to the Graveyard to activate a WATER monster's effect. "Atlantean Heavy Infantry" and "Atlantean Marksman" destroy a face-up or face-down card your opponent controlls, respectively. "Atlantean Dragoons" searches for any Sea Serpent-Type monster from your Deck, regardless of its Level, serving as the main search engine in your Deck, as most of your monsters are Sea Serpents. Also, all of them have effects while on the field.

"Mermail Abysspike" can discard a WATER monster to add 1 Level 3 WATER monster from your Deck to your hand. While "Atlantean Dragoons" can't search for cards like "Genex Undine" and "Mermail Abysslinde", this card can.

One of the strongest monsters in this Deck, "Mermail Abyssmegalo", can be Special Summoned from your hand by discarding 2 WATER monsters. While triggering up to 2 Atlantean effects, it can also add 1 "Abyss-" Spell/Trap from your Deck to your hand, usually "Abyss-sphere". And while in the field, it can tribute 1 WATER monster to attack twice. Using two can also result in a Xyz Summon for Number 11: Big Eye.

Finally, one of the cards that are used to finish your opponent is "Moulinglacia the Elemental Lord", for being searchable by "Atlantean Dragoons".

While not focusing on it, this Deck can also make use of Synchro Summons by using "Deep Sea Diva" and "Genex Controller". "Gungnir, Dragon of the Ice Barrier" is one of the main monsters to be summoned this way, being able to destroy up to 4 cards on the field by using the Atlanteans.