Bekki, so good to see you on Mudcat, again. Welcome back!
Regardless of the more mundane meanings, watery things and creatures have always held some mystery etc., though women may have related more to that and believed more than the men. As you say, even if things about them are not mysterious now, they certainly could have been, i.e. not understood, in olden days.
As to shamanic totems and spirit helpers, you will get a lot of naysayers on here. No one seems to have a live and let live attitude any more.
I hope you get more responses as to songs and ballads, etc. Have you heard Art Thieme's version of the The Great Silkie of Sule Skerry...beautiful.