Kelp hair by Arki

https://www.daz3d.com/seafolk-kelphair-for-v4-a4-m4-and-h4

is very long (and free!) and can be twisted to do the modesty thing. The colour options are limited, though, because it is ment to look like a mermaid's hair. Might need some postwork in the breast area to make the hair denser.

It's rather old and made for V4.

There is a colour expansion pack:

https://www.daz3d.com/kalypso-kelphair