Sources for underwater settlements

[Roi C.]

In our next session, my players are supposed to arrive at a large lake in the Feywild, filled with villages of merfolk, sea elves and possibly other "good" aquatic races, under the tyrannical rule of a fear mongering sea hags and her army of sahuagin, merrow and possibly other water baddies. Problem is, I'm not sure how to run the aquatic races' settlements.

Are there any sourcebooks or adventures (be it official WotC or even TSR material, 3rd party material and even stuff from other games that can be used easily with 5e) that have a friendly underwater settlement to take inspiration from? I've flipped through Ghosts of Saltmarsh and 2e's Sea of Fallen Stars, but both didn't quite offer the details I was looking for (but I might have missed them, so feel free to correct me). I'd be happy to hear any suggestions that you guys can offer.

Thanks!

[Kurt Kurageous]

I don't know any, but that doesn't stop me from having thoughts.

Underwater settlements/civilization have to contend with threats from above, making walls useless. A net is an improvement, but requires maintenance. Peace is highly desirable, and perhaps the hags are enforcing this peace by running a kleptocracy. Think street gangs running insurance and protection rackets. Think whole communities in silent terror, depressed with the hopelessness.

To confuse players about the sources of conflict, the "bad" races operate social clubs and live among those they prey upon.

[Zaltman]

This has above and below the surface encounters. https://en.m.wikipedia.org/wiki/The_War_Rafts_of_Kron

[Zaltman]

This has above and below the surface encounters. https://en.m.wikipedia.org/wiki/The_War_Rafts_of_Kron

And a good plot and sea elves.

[Naanomi]

It has been a while since I looked at it, but the 3e book 'Storwrack' may have some material. I seem to remember some of the Eberron stuff (secrets of Xendrick? City of Stormreach?) dealing with Sahuagin was good as well; but I don't recall specifically.