I think there is power in having a physical representation, though we are the waters I think we should be able to shift to some degree, but remaining formless when other spirits take physical shape is likely to make us in both the short-term and long-term less obviously there, our gifts more debatable than the gods and spirits that are showing themselves, how quickly the formed Devourer captured the minds of our worshipers. And personally our people are going to depict us as something ultimately anyway, even if we did choose to remain formless, so I'd just rather we have some say in our features.
I think the whirlpool is neat, and I do like the idea that maybe our symbols involve whirlpools/swirls, but it's quite subtle and is certainly playing more along the formless lines while giving us a shape.
I mean I'm very much pro-my own water serpent, sort of Naga form, I think it clearly keeps our elemental nature, and doesn't make us all too human, and I think the art of a spire of water twisting from the ocean against the Devourer would be cool.
Finally, I do like the kelp hair, pearl eyes, blue humanoid of many faces, though it plays strongly into my wishes towards more indeterminate gods, with shapechanging capabilities. I like the bits of consistency, but it ultimately is the most humanoid of the bunch in the running, its my favorite path for a humanoid form, but well I'm more partial to being less humanoid overall.
