Into the Drowning Deep by Mira Grant (aka Seanan McGuire's horror pen name) It has great disability rep in it but is capital H Horror ... especially if you have thalassophobia. The way she did horror mermaids was -chef's kiss-

I want anything/everything Seanan McGuire BUT her Mira Grant series, especially the Feed/Parasite ones seem like they'd do especially well & are painfully timely. Also the deep ocean monster ones in the wake of billionaire submarine disasters could be a hit. Yeah, actually I stand by anything Seanan

Boothill and Argenti. They both have similar "kinda shows up everywhere" vibes, to the point where I'd ask if they travel together.

If you want anatomically correct (and murderous) mermaids, you should check out Into The Drowning Deep by Mira Grant! It’s SO GOOD. Grant writes biomedical thrillers so her science is ON POINT