One thing people can think about is that these names don't have to be standard - ie strait, sea, ocean, etc.
They can be, but they don't have to be.
For example, it can be a name that doesn't use those, like Il Mareus Kase, or like The Maw, or even Munnen Saer-The Jaw, which are 2 names for the same body of water, just in local tongues maybe.
They can be like i've used in one of my stories - the Farmost Waters, or the Bowl, or the Serene Deeps....
I just need to put in the text, but it can be anything that describes the waters. Grey Shoals, Crystal Main, the Iron Heave, the Blue Beast, Cold Breakers...
or if there's a sea deity... Gaol's Land, Palesmelk, Mieleswaves...
or descriptive of its use - the Merchants Way, Skordpass, or whatever.
Just some ideas for alternative naming concepts.