I just watched a video that might help explain the many unexplained water crashes. I know it's helicopters, but the same physics apply in hovering.
Here is an excerpt from a supporting website -
In Ground Effect (IGE) is a condition where the downwash of air from the main rotor is able to react with a hard surface (the ground), and give a useful reaction to the helicopter in the form of more lift force available with less engine power required.

What is occuring is the air is impacting with the ground and causing a small build up of air pressure in the region below the rotor disk. The helicopter is then "floating" on a cushion of air. This means that less power is required to maintain a constant altitude hover. IGE conditions are usually found within heights about 0.5 to 1.0 times the diameter of the main rotor. So if a helicopter has a rotor diameter of 48ft, the IGE region will be about 24 - 48ft above the ground. The height will vary depending on the type of helicopter, the slope and nature of the ground, and any prevailing winds

Out of Ground Effect (OGE) is the opposite to the above, where there are no hard surfaces for the downwash to react against. For example a helicopter hovering 150ft above the ocean surface will be in an OGE condition and will require more power to maintain a constant altitude than if it was hovering at 15ft. Therefore a helicopter will always have a lower OGE ceiling than IGE due to the amount of engine power available.



Here is the video -

https://www.facebook.com/reel/1559903544848377

I just watched a video that might help explain the many unexplained water crashes.
The main reason for unexplained water crashes is flyers not providing the recorded flight data that might help explain their incident.
When data is provided, it usually shows simple reasons for the crash rather than supporting the popular myth that water upsets the drone and it just stops flying.

For example a helicopter hovering 150ft above the ocean surface will be in an OGE condition and will require more power to maintain a constant altitude than if it was hovering at 15ft.
So the helicopter hovering low over water requires less power than if it was hovering high up?
How does that say anything about drones crashing into water?
If the drone needed less power to hover close to the water's surface, how would that cause crashes?
If it was what you are suggesting, it would also cause crashes when hovering close above the ground.

The facebook video isn't saying the same thing but it still doesn't explain mysterious water crashes.
If your ground effect is lower over water, the amount of thrust required to hover is still less than when up high.
The drone has plenty of thrust available when needed up high, why would it have a problem when less thrust is required down low, whether above water or land?

Labroides Posted at 3-17 16:51
I just watched a video that might help explain the many unexplained water crashes.
The main reason for unexplained water crashes is flyers not providing the recorded flight data that might help explain their incident.
When data is provided, it usually shows simple reasons for the crash rather than supporting the popular myth that water upsets the drone and it just stops flying.

You got it backwards. Hovering over water requires more power. Without adding throttle, the craft will descend. Just something to think about. Not to dismiss out of hand.

Mobilehomer Posted at 3-17 18:29
You got it backwards. Hovering over water requires more power. Without adding throttle, the craft will descend. Just something to think about. Not to dismiss out of hand.

Hovering over water requires more power.
More power than what?
Hovering low over water requires less power than hovering up high.
The reference you quoted says that.
Hovering low over land requires even less, but no-one is suggesting that drones mysteriously fail to maintain height over land.


Without adding throttle, the craft will descend.
You should know that the drone has sophisticated systems of monitoring height and maintaining it.
The drone doesn't just sink on its own.

Despite the uninformed accounts of drones failing to maintain height over water, this isn't supported by any evidence.
Why is it that the folks that insist on pushing the myth can't show flight data to support it?

Flying a drone low over water could possibly mess up the downward/landing sensors. And that's a reason why people crash when flying over water.

Killerbee Posted at 3-18 08:49
Flying a drone low over water could possibly mess up the downward/landing sensors. And that's a reason why people crash when flying over water.

Yes, people claim that all the time (like the OP has).
But they are people who don't understand how their drone works and don't read flight data.
They say it because they've heard it , but it's just a myth.
"Messing up" the downward sensors doesn't cause drones to descend uncontrollably.

Killerbee Posted at 3-18 08:49
Flying a drone low over water could possibly mess up the downward/landing sensors. And that's a reason why people crash when flying over water.

Hi,

Sometimes the autolanding ** function makes the drone descend..as in a normal landing.
** IR height 0.5 meter (true or false reading) + stick down for short moment will initiate an autolanding.

If you not aware of this than pilots most likely (for 'sure' if drone is out of eye sight) too late to give a UP stick to cancel de autolanding.
Not a drone fauilure....but a pilot fault.
But DJI changed already this a bit in N and C mode...flying low with speed drone will not descend on down stick. (but does in Sport mode!)

Flying low (and fast) over streaming water is tricky, when IR height data is On-Off measuring and the vision does not get a stable picture...few cases i have seen that drone will loose height.
Not only seen in others logs, but my own experience too.

So no myth, but it can happen! So my advice : always keep an sharp eye on your drone when flying low over water.


cheers
JJB

Labroides Posted at 3-18 12:12
Yes, people claim that all the time (like the OP has).
But they are people who don't understand how their drone works and don't read flight data.
They say it because they've heard it , but it's just a myth.

Oh, it's not a myth.
Back in the days when we flew our Mini 2 drones low over water, we had to stick some tape over the landing sensor to keep it from autolanding in the water.

Killerbee Posted at 3-18 13:00
Oh, it's not a myth.
Back in the days when we flew our Mini 2 drones low over water, we had to stick some tape over the landing sensor to keep it from autolanding in the water.

I doubt that  ... flyers in forums have been convincing each other, but without any evidence to support it.
Care to provide any flight data that might show that I'm wrong?

Labroides Posted at 3-18 15:29
I doubt that  ... flyers in forums have been convincing each other, but without any evidence to support it.
Care to provide any flight data that might show that I'm wrong?

I don't have any hard data. But that doesn't mean something is a myth.
You can doubt as much as you'd like, I don't really care.
I know for myself what I've seen and experienced, and I can show you in these clips.
But you'll probably still have doubts after seeing this, maybe you should generate your own flight data.

Killerbee Posted at 3-18 21:33
I don't have any hard data. But that doesn't mean something is a myth.
You can doubt as much as you'd like, I don't really care.
I know for myself what I've seen and experienced, and I can show you in these clips.

I don't have any hard data. But that doesn't mean something is a myth.
Likewise, just because many believe something that doesn't make it true either.

But you'll probably still have doubts after seeing this,
Yes .. I remain unconvinced.
Seeing someone guessing without seeing what's actually happening doesn't do it for me.
The common myth involves the sensors acting up and causing loss of drones, but one of those guys is guessing the other way (without a shred of data to support his guesswork).

maybe you should generate your own flight data.
I do .. all the time because almost all my flying is over water and it doesn't show water acting like a magnet and sucking the drone downwards..
I'm just back from 47 km of overwater flight today.

Try flying a few inches above the water, hover a bit and see for yourself.
It's hard trying to convince ignorant people like you, so I'll just rest my case.
Happy flying!

Killerbee Posted at 3-18 23:30
Try flying a few inches above the water, hover a bit and see for yourself.
It's hard trying to convince ignorant people like you, so I'll just rest my case.
Happy flying!

Try flying a few inches above the water, hover a bit and see for yourself.
Why would I do something stupid like that?

It's hard trying to convince ignorant people like you,
Ignorant  huh??
I wouldn't attempt your ridiculous challenge because I'm aware of how DJI drones work.
Look at the specs for any model and you'll find something like this:
Hovering Accuracy Range
    Vertical:
    ±0.1 m (with vision positioning)
    ±0.5 m (with GNSS positioning)

Unquestioningly accepting and spreading myths without looking for evidence to confirm their validity (or not), is the very definition of ignorance.

If you want to leave out your attempted insult, it would be easy to convince me.
All it would take is evidence in the form of recorded flight data.
There's no shortage of myth believers like you, but it's been very difficult getting anyone to share flight data from some of the " many unexplained water crashes".
So far the few examples that I've been offered turned out to have other  simple identifiable causes and did not confirm the widespread myth.

Dude, this whole discussion is about flying close over water. Like in really close.
What did you think I meant with close over water....30 feet? That's not close.

You're the only person here calling things a myth.Again, I said it before but you are ignorant, I've seen and experienced with my own eyes what happens when you fly a drone low over water. And by low I mean 3 feet and lower.
So, for me it's not a myth. It may be a myth to you, but I'm guessing you're flying your drones nice and high up in the sky. Up in the sky it doesn't matter what's below your drone.
The landing sensors don't see what's below when you're high up in the sky. The windflow that your props generate up in the sky doesn't even touch ground, so it doesn't matter if it's land or water.

That makes much more sense! Now I know whenever I fly over water I will add some extra throttle.

Killerbee Posted at 3-18 23:30
Try flying a few inches above the water, hover a bit and see for yourself.
It's hard trying to convince ignorant people like you, so I'll just rest my case.
Happy flying!

Thanks, now my DJI Tello has been water damaged (I tested it with a Tello because they are cheaper). I'd happily take you to court if I had your email.