Mermails (also known as Mermail Atlanteans) are a toolbox deck that focus on taking advantage of Atlantean monsters’ effects with the effects of Mermail monsters. Most Mermail monster effects involve special summoning or searching by discarding a Water monster, while Atlantean monster effects involve destroying face-up or face-down cards on the field when discarded by a Water monster. When the two archetypes are combined, it has lots of potential to end games quickly by swarming the field and outing cards on the opponent’s field respectively. Mermail Abyssteus is the main monster of the deck, which both special summons itself by discarding a Water monster and searches out a level 4 or lower Mermail monster. Mermail Abyssmegalo is the main boss monster of the deck, which also special summons itself by discarding 2 Water monsters, searches an 'Abyss' spell or trap, and has the potential to attack twice by tributing an ATK position Water monster. Atlantean Heavy Infantry and Atlantean Marksman are the main 2 cards to discard with Abyssteus / Abyssmegalo, destroying face-up cards and face-down cards respectively. Combining these factors with Deep Sea Diva, which summons an Atlantean from the deck, and you have a ton of versatility in terms of plays that you can make in a game.
Because this deck has been out of the meta for a while, we do not have enough statistics on the deck to generate an up-to-date breakdown. See below for the most recent available decklists.