I have recovered 2 drones from water crashes by running float kits.
A Mavic Pro, and a Mavic 2 pro.
Both worked great after they were dried out. and are still flying today.
Luckily it was fresh water each time.
If not for the float kit I would have lost each of them and the sd cards containing the footage I was shooting.
Side note, as risky as some people may think it is I have done dozens and dozens of water landings/takeoffs with my float-equipped drones, I have with airplanes as well. Landing an airplane on the water is one of the most fun things I have ever done.
Here is a video from my Mavic Pro crash in the Dora cannel.