Notes & Combos
Atlantean Package:
Standard package. I would switch Infantry to 3 copies versus marksman as it's a lot more useful, especially when needing to protect your barrier statue. I also run marksman cause each current meta deck has a spell/trap that they set so it's good to force it out.
Techs
Barrier Statue of the Torrent: Very strong in this deck. I would mostly summon this through the grave with Abysstrite, the Atlantean Spirit after using it to discard for other water effects and it'll be at 1600 ATK/DEF. Deep Sea Minstrel: I only think you need one cause it's searchable with Atlantean Dragoons. It's rarely a starter and kind of a win more card. Butterfly Fish: A good card for extension because it's searchable off mermail abysspike and just allows you to be more flexible when activating your level 7 water monsters who have to discard from hand + Mermail Shadow Squad's discard effect.
Extra Deck
Only the level 10 synchros came up for me cause of Icejade Gymir Aegirine. Majority of the duels were just using the Atlantean/Mermail xys. Marincess Coral Anemone also comes up a lot to special summon either the water barrier statue or mermail squad.