Hi all,
I had a problem with my Spark a few days ago and it crashed into the sea. We pulled it out in a few seconds but some damage was clearly already done.

How it happened
I was taking off from a boat and as soon as the drone went over the side of the boat, it descended into the water immediately and wouldn't respond to controller input to ascend. It all happened very quickly as it was only about 1-2m above the water surface at time of take off. I suspect that some sensor confusion made it try and maintain altitude above the sea floor rather than the water surface. I have flown over water quite a lot and have never had this problem before, but I usually fly in sport mode and this time the drone was not in sport mode, maybe that was a factor. A friend with a Mavic Air experienced the exact same behaviour over a pond during the same trip.

What I did after the crash
the drone was off when it was pulled out of the water. I immediately pulled the battery, and left the drone to dry out for a long time with sun and in a rice bag. I then tried to power on the drone with a different battery - it powered up, but all 4 LEDs were red and it wouldn't connect with the controller.

I left it a few days until I got home, then opened it up and cleaned it out with electronics cleaner and compressed air. I put it back together and powered it up but it still has 4 red LEDs. There is no obvious sign of significant damage in the drone - nothing burnt up and I've cleaned up a lot of the dried salt. I didn't take the motherboard off as I think one of the connectors needs to be glued back on so I just cleaned from the top. I know there is metal cladding on the other side of the board so am hoping that protected the components on the underside.  Here's a photo of how far I opened it up and cleaned: https://i.imgur.com/ZyRZqid.jpeg  
I also noticed that when the drone is off, the props don't spin freely like they normally do, as if the motor is still engaged.

Do you think there is anything I can do at this stage to get the drone working?

Secondly, is there any sort of claim I can make since the drone force landed itself in the sea for no apparent reason?

Hi, redmonster. Thank you for reaching out, and we're very sorry to hear about the accident with your drone. In this case, the best thing to do is to send the drone back for a proper diagnosis and repair. You may submit an Online Repair Application directly, or you may contact our Customer Support at (support.dji.com) for more details about the process. Please note that warranty service can be applied if it fits the two main criteria which are the following:
1. The drone should be within its warranty period.
2. The accident was caused by a non-pilot error.
We hope that this can help you decide on your next steps. Should you have further concerns, please reach back here at DJI Forum.