Not a book, but it sounds very similar to an Outer Limits episode. Maybe that's what you're thinking of.
The nanobots cause his body to "adapt" very quickly to any environment. A scene that freaked me out as a kid was when he was in this water tank for some kind of test or whatever, and the nanobots caused his body to develop gills.
The nanobots cause his body to "adapt" very quickly to any environment. A scene that freaked me out as a kid was when he was in this water tank for some kind of test or whatever, and the nanobots caused his body to develop gills.
https://www.imdb.com/title/tt0667978/