My rendition of Atlantean Mermail. The deck is still a 1 card OTK with Deep Sea Diva, but this is my expanded version of it where in theory you can do more things before OTK'ing.
Coral Anemone is probably the best bridge/recycler in the deck. Needing no specific statlines to summon, you make her with any two Water monsters but she gives you access to just about anything you need. You will be summoning back Neptabyss or Heavy Infantry for the majority of the time, Neptabyss usually to tribute it with Abyssmegalo to then revive Dragoons, reviving Heavy Infantry can let you get a second normal summon so if you have a second Deep Sea Diva you can continue your combo then.
Minairuka is one of my new favorite cards in water decks after testing it out, its ability on the field is basically non-existent but serves instead as a way to chain block your important cards from being ashed. Normal Deep Sea Diva, activate effect of DSD then chain Minairuka as CL2 to protect her from Ash Blossom. It really is more or less just Ash "Insurance" but comes up so much more often than I ever thought it would. Also serves as a good body on the field to make Dweller using it and Dragoons then triggering Dragoons again.
Icejade Ran Aegirine is another good starter despite it locking you into waters while you control that token, since you make Icejade Gymir Aegirine, Chengying, or Coral Anemone with her and the token. It's essentially the 2023-24 version of Abyssteus but better.
There's an unbelievable amount of lines the deck can cycle through but due to the extremely linear gameplan the deck has always had you should expect to lose more than you win in Best of 1 scenarios. The deck lives and dies by the side-deck since every interruption since 2017 has basically corkscrewed the entire gameplan. Even a well timed Veiler can completely kill the objective of playing Atlantean Mermail.
But overall this is the version i'm happy with, the right amount of utility and thinning, the ability to chainblock, strong bosses still makeable (Baronne, Cheng, Gymir, Dragite) and of course the fact that it's still Atlantean Mermail- the deck excels in getting the job done and the game over as good as it did when Neptabyss came out.