Woohoo! Yas :>

This is less related to Norse gods and such and more a part of folk lores, like in my country (and other Nordic countries too I assume) kids are often told not to swim too deep into lakes "so that the Näkki living in the lake/river won't take you away". Kind of sinister when I put it like that but at least it was a cool story to hear as a child and I think I actually feared the mythical creature because of it. Didn't drown tho, so I guess it worked lol
ps. I say Nordic because if you nitpick, Scandinavia only includes three Nordic countries but you get the jist xD