i wish that a new aquatic transformation and a ocean expansion were the new transformation, expensive clothes, or swimming maxed make exploring easier. depended on how much you believe transformations are real or are just costumes, i can see 2 options for a aquatic form, a tentacle(real)(holy) or a dolphin(costume)(animal).
tentacle i would like to add extra tentacle "hands" that can be used in encounters and have a "connection" to tentacles and can enter/exit "their" plane at will with any door, with the minor restriction that the emergency exit is deep in the sea and the other must be found if available (no going out of your mirror unless its 3AM) and a heavy hit to stress and trauma when used in public and a massive one if used in a encounter with people or bad ends that involve people, instead of a skill like other transformations they get 3 orgasms per part at a max of 9 with the tentacles getting more "close" that you aren't a pure tentacle, after the last one the next orgasm start a encounter with max tentacles in play, with the rest of the kit being the based around lasting a bit shorter under sexual situations , having a powerful stress reliving orgasm being quite useful not to blackout after stuff like gang rape but unlike demon no way to remove trauma, and being anything but the most aware is stressful(like demons and purity) plus stat bonuses for swimming.
the dolphin is akin to other animal transformations being more bonus oriented rather than a insane change like the tentacle with the buff being swimming and air retention(staying not getting knockout because of strangulation)
robin events for both would be playing with the tentacles for the tentacle and touching your fin for dolphin
i would love to see the tentacle be added but I'd be happy the dolphin and more exploration into the seas depths
edit: i got a idea to add on to the dolphin, a fatigue reduction for travel at night at the cost of time because dolphins sleep with half of their brain awake