Looking for a novel about a woman who gets her hands replaced with super long fingers and goes off-world to a water world to solve a mystery.
Carol Severance's Reefsong?
After narrowly escaping death in a forest fire, Angie Dinsman found herself under the control of the World Life Company. They promptly equipped her with webbed hands and gills—creating a half‑fish, half‑woman. Her mission is to uncover secret research files on the water world of Lesaat. But first she has to undergo the terrifying process of learning to breathe underwater. After mastering the basics of survival, she faces an insurmountable challenge: finding the information that could end starvation on Earth while sabotaging the company's evil plans.
Found with a search for
site:goodreads.com hands replaced water world