I live in Key West and run a Marina here. I have been around salt water for a long time. Being that said please don't give up hope after what I am about to say but salt water is a terribly corrosive thing. Even if you do manage to rinse off the components and get the device back working it seems like a matter of time and problems will still occur. We have had several items fall into the water including waterproof radios, computers, cell phones, and drones, all to no avail eventually. They all don't seems to survive the dip in the water, even if it's brief. Again, saltwater is a very bad thing when you mix it with anything electrical.
I'm not saying you can't bring your drone back from the dead but in my experience, replacement is the best route. Good luck.