I'd like to preface with the following:

• My "fleet" of RC Aircraft Consists of 3 RC Helicopters (2 collective pitch), 8 Quadcopters, and a full suite of FPV gear
• In addition to the above, I own 2 DJI Sparks and a variety of related, official accessories. One of the Sparks suffered a RTH accident a year ago, so I only use it for short, on-land demo flights.
• Having been one of the users who experienced a completely random "drop out of the sky" event almost a year ago, I have a pre-flight routine I go through, especially since I frequently launch off of a boat and fly over water. This routine includes: Battery Check (check contacts for corrotion, charge level, properly "clicked" in to the Spark), Propeller Check (blades in good shape, none of the plastic tabs broken), GPS Lock Check, Sensor Check (front and bottom), etc. I generally try to land between 50% and 35% battery.
  

Last weekend, I captured a handful of videos like this:

You'll notice the quality is low, because these are from the cache on the tablet.

At the very end of the day, we were preparing for a final shot when I launched the Spark, switched to Active Track, then attempted to initiate a "Dronie" video. Immediately upon initiating the Dronie, we heard the propellers begin to oscillate - as if the Spark were struggling under its own weight. It then descended in to the water, never to be seen again. There were no errors, no warnings, nothing.

The flight log: http://www.phantomhelp.com/LogViewer/UFWAR84WPRP0PYONBNDE/
And here's the DAT for those interested: https://www.dropbox.com/s/3wjzv7 ... -38_FLY261.DAT?dl=0

I'm incredibly disappointed and not sure whether to be upset at myself or at DJI.

Welcome to the club...one of my drones also rests on the ground of a lake.

It looks as if you may have gotten too close to the water and was not ready for the "VPS dip".
The Visual Positioning System does not like reflective surfaces.
All it takes is a second to look away to tap and set the dronie (or any other) to look up just in time to see the Spark begin to dip but too late.
I had this happen once before and I am glad I read about it first.

Now I see you were lower in some places on the lake...was it partly cloudy?
Darker reflections while closer to 6ft of the water may not affect as much as bright reflections 18ft away.
Plus VPS said you were 10ft at the end.

But at 7:00:0.1 you got an "NA" in the middle of 13.5ft at 7:00:0.0 and 7.2ft at 7:00:0.2
That may be your proof the VPS was being messed with.

By the way, that random falling out of the sky last year was a battery firmware issue from what I read.

I am sorry to hear the mishap, that must be frustrated for you. For this case, please contact our support to start a ticket, we will help to make data analysis if the drone is under warranty period (within 12 months old), if it's a warranty case, we will compensate the drone according to After-Sales Policy.
Here’s the link to contact us: http://www.dji.com/support

Not sure if it is 'the cause' but water / reflective surfaces will fool the bottom sensors (VPS).
I have seen this happening over grass in bright sunlight also with my MP. The drone started to descend and I had to push the controls to rise again.
I have not tried active track, but I'm not sure if that might cause for an extra factor to make things complicated for Spark.
As you got lower to the surface, the VPS will kick in (you can see in the flight log it started to register altitudes, but fails from time to time).

Sorry about the incidence. I agree with pmshop, could be the VPS since Spark cannot turn them off (like Mavic Pro). And if you read the manual from DJI, they actually did say if you fly over the water with Spark,  it might mess up the VPS. You can see some more of the warnings here in which I collected from DJI documents.
https://forum.dji.com/thread-109501-1-1.html

pmshop Posted at 2018-6-11 17:08
It looks as if you may have gotten too close to the water and was not ready for the "VPS dip".
The Visual Positioning System does not like reflective surfaces.
All it takes is a second to look away to tap and set the dronie (or any other) to look up just in time to see the Spark begin to dip but too late.

Yup, that's probably it. I was able to recover a few seconds of the very last video but apparently I'm not allowed to link to Dropbox, and YouTube doesn't like the video (showing as unplayable, even though it plays locally and on DropBox).

It's very rare that I use any of the "Quick Shot" modes so I suppose I've just never run in to this before - and sadly I seem to have missed any discussion around the "VPS Dip" you're referring to. Of course, turning off VPS is not an option on the Spark. I'm aware of DJI's warning about reflective surfaces, however I don't recall them specifying a minimum or "safe" distance, if any.

Depending on the response from DJI I'm still trying to decide whether I'm going to continue investing in DJI products of if I'm going to have a fire sale for the accessories I have left.

mmatos Posted at 2018-6-12 06:05
Yup, that's probably it. I was able to recover a few seconds of the very last video but apparently I'm not allowed to link to Dropbox, and YouTube doesn't like the video (showing as unplayable, even though it plays locally and on DropBox).

It's very rare that I use any of the "Quick Shot" modes so I suppose I've just never run in to this before - and sadly I seem to have missed any discussion around the "VPS Dip" you're referring to. Of course, turning off VPS is not an option on the Spark. I'm aware of DJI's warning about reflective surfaces, however I don't recall them specifying a minimum or "safe" distance, if any.

Like Phuong Do posted, there really is not a safe distance stated.
That is why I posted the different scenarios - overcast might affect much closer than bright days that could be affected at higher altitudes.

When saw my first "VPS dip" flying over water, I was looking right at it and was able to react fortunately.

Not tooting DJI's horn but I would stick with it.
I have had issues in the past (no GPS home point set with in reasonable time, gimbal not holding the horizon, YAW issue) but for a good "all-in-one package" Can't beat the Spark.

Plus, they are down to $350 for new - $279 DJI certified refurbished?
Same refurb as you would get if you are part of the DJI Care Refresh program.

Phuong Do Posted at 2018-6-12 00:40
Sorry about the incidence. I agree with pmshop, could be the VPS since Spark cannot turn them off (like Mavic Pro). And if you read the manual from DJI, they actually did say if you fly over the water with Spark,  it might mess up the VPS. You can see some more of the warnings here in which I collected from DJI documents.
https://forum.dji.com/thread-109501-1-1.html

Just curious as to what "close to water" is. how many feet above?

GOSpark Posted at 2018-6-12 07:46
Just curious as to what "close to water" is. how many feet above?

I hate to be crass but when you see it dip, you are too close.

Different conditions will make the effect change altitudes.
Like I said, when it is overcast, you may be able to get close without the effect happening than you would on a bright day at higher altitudes.

I can say this, I saw the effect at approximately 10 feet, overcast and thinly treed canopy environment

Always best to keep at least 2m above water and switch off VPS

A CW Posted at 2018-6-12 11:13
Always best to keep at least 2m above water and switch off VPS

2 meter not enough . Atleast 30 to 40 meters is a safe altitude near water

Or in Sport Mode (which disabled VPS) on my recent feat (1:50mins mark)  

S.J Posted at 2018-6-12 17:59
2 meter not enough . Atleast 30 to 40 meters is a safe altitude near water

Higher the better but DJI advise at least 2M

Awesome Video !