I was flying my spark over the Gulf of Mexico, and when flying parallel to the beach, it suddenly lost 10ft of altitude, went below line of sight, and plunged into the water. What should I do, it's been almost a year since I bought it.
Edit: Here is the log: https://www.phantomhelp.com/logviewer/3YGA0ROVZ99ZZG8MK6XE

Hello there 0Stephan. I am sorry to read and to know what happened to your DJI Spark. Since this unfortunate happened I would recommend you to contact our DJI support team at https://www.dji.com/support?site=brandsite&from=nav for further assistance.  We have a professional team that will do there best to check what happened to the said drone and will give out the best resolution for this issue. Again I am sorry for the trouble and thank you.

Hi Stephan,

Sorry for your loss.
Please upload your flight logs (they are on your phone or tablet you used) here:
https://www.phantomhelp.com/logviewer/upload/
so we can analyze what happened.

Cheers,
Wolferl

Where was the RTH mentioned in the title? And what sensor error? There is no technical fault of any kind in the log. The sudden interruption of the logging, suggests that there was a power interruption, which could have been due to the battery running down. Unfortunately, this is a common fault with Spark and it happened to me, but not when new, it must have been about 1-1.5 years old. by that time the battery retaining lugs have worn a bit. It also happened to me when I suddenly changed direction in Sport mode, just like you did towards the end of the flight. Several minutes of flying with quick turns and then a sharp change of direction and the battery died. Look it up, there have been many such cases. No solution, buy a new one. It's no coincidence that DJI used a different battery mounting solution on their new drones...

Jakab Gipsz Posted at 7-25 12:53
Where was the RTH mentioned in the title? And what sensor error? There is no technical fault of any kind in the log. The sudden interruption of the logging, suggests that there was a power interruption, which could have been due to the battery running down. Unfortunately, this is a common fault with Spark and it happened to me, but not when new, it must have been about 1-1.5 years old. by that time the battery retaining lugs have worn a bit. It also happened to me when I suddenly changed direction in Sport mode, just like you did towards the end of the flight. Several minutes of flying with quick turns and then a sharp change of direction and the battery died. Look it up, there have been many such cases. No solution, buy a new one. It's no coincidence that DJI used a different battery mounting solution on their new drones...

RTH--In the case that the connection between the drone and rc was interrupted, the drone should have returned to the launch area.
Battery was at 60%+, and I have not found any of the mounting points on the battery defective.
Sport Mode--I usually get around 12-14 minutes of sport per battery, if used only for that. This flight was terminated less than 6 minutes in by the drone dropping 10 feet into the water.
Neither of my 2 batteries have been over 35 charges yet, and it hasn't even been a year since I got the drone.

Hi Stephan,

You were flying very low over water, just 4 ft. Could have been a drop of water from waves that knocked your Spark out.
I do not see anything gone wrong with your Spark on that flight.

HTH,
Wolferl

Wolferl Posted at 7-27 04:22
Hi Stephan,

You were flying very low over water, just 4 ft. Could have been a drop of water from waves that knocked your Spark out.

I was flying at 12 feet, and then something caused it to drop to 4 feet. I did not lower the drone to that height.

0Stephan Posted at 7-27 04:52
I was flying at 12 feet, and then something caused it to drop to 4 feet. I did not lower the drone to that height.

Hi Stephan,

Flight altitude is controlled mainly by barometric pressure sensing, thus being inherently dependent on air temperature. We all know how air temperature feels cooler on water.
Downward infrared sensing does not work on water surfaces.
Usual GPS is by far not precise enough for exact height measurements.

Cheers,
Wolferl

0Stephan Posted at 7-25 15:33
RTH--In the case that the connection between the drone and rc was interrupted, the drone should have returned to the launch area.
Battery was at 60%+, and I have not found any of the mounting points on the battery defective.
Sport Mode--I usually get around 12-14 minutes of sport per battery, if used only for that. This flight was terminated less than 6 minutes in by the drone dropping 10 feet into the water.

In this particular case, there can be no RTH, because the connection was perfectly good throughout the flight and you did not manually initiate RTH.
That is why I asked where was RTH?
My colleague Wolferl may be right, but it may also be what happened to me: in a flight, when instructed to climb, it started to climb and it was not possible to intervene. It simply landed, but in the end it did not slow down and all the rotors on the concrete broke because it overturned. (There had been several problems before that on take-off. It bounced, climbed in steps, sometimes slid back.)
That could have happened here. In the Spark, after a while the connections oxidize and cause power supply problems (and control anomalies). If you imagine the battery voltage decreases when flying over water, with decreasing voltage you need more current for the same power, but oxidation doesn't increase it. Then, according to the formula P=U*I, if U (voltage) decreases and I (current) cannot increase, then P (power) will decrease. So the Spark starts to sink, but there is water...
The sudden interruption in data recording suggests that it has gone underwater.
I repaired mine after a hard landing and it stopped bouncing and landing and drifting due to lack of power:
https://forum.dji.com/forum.php?mod=viewthread&tid=220364

Update: DJI has put this as a warranty claim and have sent me a new Spark.