We have seen a bunch of interesting waterproof drones in the past. Rutgers University is working on a drone that can fly and swim reliably. It can be used for search & rescue, monitor oil spills, and even defuse underwater mine threats. The below video shows how this drone performs:
As Javier Diez, a professor in the Department of Mechanical and Aerospace Engineering, explains, there is still much work to be done. More information is available here.