I just think that the whole thing with Hela was ODD! I think they should have made it that she was Loki's mom. <<I was actually kinda hoping she would be his mom, too, but I think the sister thing works as well. It's new and fresh, so I'm not complaining.
It makes sense though. In the (which Legend of Korra is assumed to be set in) the first real swimsuits were made. In Avatar the Last Airbender they didn't have a defined swimwear so they wore whatever.