Hmmm~

I really like the general idea here. I'm trying to think of how it would work. Marine houses are a good start, but for players who may not want to commit to that, maybe there could be a minor house upgrade that allows them to have 1 - 2 aquatic pets in whichever house part it's placed. And it could be a removable upgrade, but of course the aquatic pets have to be removed beforehand.

I'm gonna think about it some more and I might post again, but either way I do really want more aquatic pets in the future! At the moment we have Sealott, and that's a cool pet, but there are so many other neat critters in the ocean to draw inspiration from.

Maybe for aquatic pets players could pay an additional cost to add a pool to the home? like, it would take up part of the back yard, but they could place a pool/pond of a size of their choosing increasing w/ each slot? like a base 1x1 could be something like 20 - 30PC, then increase by 5 w/ every 2 additional tiles (rounding down)

So for example a 2x2 is 4 tiles, so if we say its set at 20 for a standard 1 tile, 4 tiles would be 25PC

I'm all for this
Maybe an item that would be like a kiddie pool for inside the house too? Sort of how you can stack pets on tables and such, only mandatory. I'd be quite excited for a jellyfish or octopus pet!

For the pets, I think it would be simpler to go Flying Seafood Special.
But water-themed decor sounds nice as is.