With Scrypton added to TCG (idk about OCG tho), it makes Formud Skipper a must use in Marincess. Not only it acts as extender itself, Scrypton recycles the banished together with Marincess Great Bubble Reef. I will explain both Blue Tang and Formud route (both still needs extender tho).
Normal summon Blue Tang, dump Sea Horse (or Mandarin if you alrdy have Sea Horse), make Blue Slug add Sea Horse from GY, ss Sea Horse make Sea Angel add Battle Ocean. From here we need another extender to continue with applied Crystal Heart. Ss the extender, make Coral Anemone (if you wanna recur your Marincess in GY or if you wanna make a link 4) in extra zone, make Crystal Heart, place field spell (always place field spell when you're about to make your last big monster with Crystal Heart), ss any big link Marincess monster (Marbled Rock if first turn, battle protection, and can recur your resource too; Great Bubble Reef to recur banished or in GY Marincess; Wonder Heart to OTK if locked to water; Accescode via Splash Mage - Transcode route for optimal OTK).
The Formud route, normal summon Formud (or via one for one), use Formud choose any Marincess in extra deck, make Sea Angel, add field spell then Scrypton from Formud, ss Scrypton make Coral Anemone, use Coral ss Sea Angel. From here we need extender to continue. SS extender, make Blue Slug (you can choose not to use its effect so the big link will have more equip later), then make Crystal Heart so we have enough material for link 4 (Marbled Rock is preferred despite it's a link 3).
I only run 2 Pascalus because we run many other extender which are not its target, 1 Mandarin because its condition is kinda situational. The rest is just extender or staple with the trap lineup to turbo out Marincess Wave since Blue Tang cant search it consistently enough while still running another great target for Trap Trick.
Pros: Super consistent, big immune body, great recursion, bunch of handtraps, and can even run Deep Sea Minstrel (to snipe oppnent's handtrap).
Cons: Standard board is just big immune tower with no interruption, sometimes water/cyberse locked
Cards to think of: Frog lineup (Marincess is a 2 cards combo, so adding another 2 cards combo engine conflicts with each other), Mermail Abyssteus-spike engine (it searches Sea Horse, but needs 2 water discards, at that point we could combo with those 2 cards instead of running this engine), Kaiju (Gameciel is a must for side deck), Abyss Dweller (great card, but needs consistent Pascalus to make it, and most deck can still play around Dweller easily).