Hello, I purchase a P4 recently and took it on a beach vacation. I also have a P1 version so, I think I have enough experience in flying the Phantoms. Well, while flying the P4 over the beach on I heard a beeping sound so I hit RTH but I notice it was just hovering and not moving but then all of the sudden it started going backwards without touching the stick. As I listen,  the frequency of the beeping was getting stronger so, I tried to take control of the stick but it's too late the P4 started to loose height until it drop down from the sky. It fell in the water for about 7-10 sec. before we able to bring it up in the surface. We shut everything and wash it down with regular tap water to wash off the sea water. We let it dry for 3 days to make sure it's thoroughly dry. After the 6th day I turn it on with a different battery and it turned on and it connected to the DJI apps. I tried the throttle and the engine would rev up as if nothing happen. The video came on for awhile but it turned off.  I only had it for less than 2 months and I did not get any DJI Care. What are my options?

I'm sorry for your crash, can you please sync your flight records and provide your email and I will look at the flight log.
Also, using the DJI Assistant2 software, connect the P4 to your computer and download the DAT files from the aircraft and upload the last flight via Dropbox or whatever online storage you use.