#onphibian

Well, I am not way a person with enough lore knowledge to give a canon supported answer, but as for my speculations? Sure, let’s think about it.

First of all, I presume TES oceans to have like, the basic variety of things we can also find in our oceans: fish, marine mammals, reptiles, shellfish, corals and so on. Probably differently named and most likely differently looking, but you got the idea. At least I hope I explain the thought well enough. 

Second I also believe that TES oceans will have, like, gigantic versions of some animals for sure. Like, giant sea serpents we can see in ESO and that seem to have strong connections with Pyandonea. Or that giant crab shell in Ald’ruhn? Imagine what a TES version of, say, Kraken can be? 

Speaking about the deeper ocean… Well, I would imagine there to be lot of bio-luminiscent animals, because it would look cool and so why not. Maybe some semi-alive plants too? They have spriggans up on earth, so maybe there are some coral based one too, or something like that? Also I would love, simply love to see like, giant isopods of TES oceans. Crawly babies from the depth below. 

What else? Well, some magic based beings I presume. Like, we have seen Nereids in ESO and various atronachs types in games and Mother Wisps and spriggans and so on, so it would be weird to me, to presume that there are nothing like this in the deeper water. Just imagine, like, ice atronach in some cold frozen oceanscape. Cool!

And as for the fishmen… Well, there are Sea Elves, Maormer, who seem to be a bit “fishy”, but given that we hardly know anything about the Pyandonea (me at least) and about them in more details some generic info, so…They seem to have some interesting magic, so maybe some of them can use it to like, adapt themselves even further for living in water and like, pull reverse Ariel thing. 

Also I remember Dreugh lived underwater or at least was somehow related to it? Maybe there are some Dreughs too.