A Mermail OTK is easy to pull off. First summon "Deep Sea Diva" and use her effect to special summon "Atlantean Marksman." Next you discard two water monsters from your hand to special summon "Mermail Abyssmegalo". Tribute "Deep Sea Diva" to have "Abyssmegalo" attack twice (make sure its a direct attack). Then attack your opponent with "Atlantean Marksman" and Special summon "Atlantean dragoons" for the finishing blow.
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