I've read here that many people recommend turning off auto landing when flying low over water, to prevent the Mavic from accidentally descending into the water. But I'm having trouble finding where this setting is in the app.

This doesn't answer your question, as I'm only semi-new to the whole drone world myself. But I'd also recommend turning off your bottom senses when flying over water. It's something a few of my drone friends have done in the past and has saved their bank a bit of a bash..
Good luck!

This should help:

https://store.dji.com/guides/dji-go-4-manual/4/

Its not auto land they are turning off but the downward facing sensors.
Water and shinny surfaces cause them to judge distance incorrectly so if you were a couple of meters above the water it might think its much closer and try to auto land into the water.

From the side menu its listed under Visual Navigation Settings > Enable vision positioning  ( I think )

Lukas_Scowen Posted at 2018-1-21 19:56
This doesn't answer your question, as I'm only semi-new to the whole drone world myself. But I'd also recommend turning off your bottom senses when flying over water. It's something a few of my drone friends have done in the past and has saved their bank a bit of a bash..
Good luck!

Those were the good old days. You don’t need to turn off anything. I fly over water regularly and don’t turn anything off. Just stay a safe distance above the water.

That feature is not on the Mavic. Because you don’t need to do any of that. Phantom series yes.

Woe Posted at 2018-1-21 20:40
That feature is not on the Mavic. Because you don’t need to do any of that. Phantom series yes.

Really? each time I fly over water I get sensor warning. I'll show ya next time, maybe a problem?

Here's a video from Ed Ricker, where he puts "Turning off the Downward Vinson Sensors while Flying Over Water" theory to the test.

To do this - disable "Landing Protection". Be careful though, when you want to bring it in to land, descend very very s l o w l y .

Tango_B Posted at 2018-1-22 23:06
To do this - disable "Landing Protection". Be careful though, when you want to bring it in to land, descend very very s l o w l y .

I'm sorry, why would this help in this situation?

Simmo1 Posted at 2018-1-22 23:29
I'm sorry, why would this help in this situation?

Disabling Landing Protection is the correct answer, and disabling it helps because it'll prevent the Mavic from landing in the water when the pilot pulls back on the throttle while VPS / bottom sensor indicates that the Mavic is near the ground. As long as Landing Protection is disabled, negative throttle will only reduce the Mavic's height, but when it's enabled negative throttle can cause the Mavic to go into landing mode and continue descending without further stick input.

Simmo1 Posted at 2018-1-22 23:29
I'm sorry, why would this help in this situation?

"Disabling Landing Protection is the correct answer, and disabling it helps because it'll prevent the Mavic from landing in the water when the pilot pulls back on the throttle while VPS / bottom sensor indicates that the Mavic is near the ground. As long as Landing Protection is disabled, negative throttle will only reduce the Mavic's height, but when it's enabled negative throttle can cause the Mavic to go into landing mode and continue descending without further stick input."

This.

Where can I disable landing 'protection' for Mini2?
My drone tried to make sucide in Cetina river one week after I bought it. That unexpected descend shocked me so much that it already touched the water after I started to pull it up. Luckily no damage remained. It might have been a different story in sea water.
I struggle a lot with the menu of the dji app because some features are only adjustable in certain circumstances.
I wouldn't be surprised that I didn't find how to turn off landing protection because I was not in flight mode xyz or missed something else.
This is one of the reason why I didn't do a seaside shot at the Kalithea springs today. A pity.

Chilli