How the Apple Watch Ejects Water


Hello, the internet. I’m Gav, that’s Mo, and welcome to this quick and dirty episode of The Slo Mo Guys. Due to my occupation, I often find myself going through life thinking, “Ooh, I wonder if that would look good in slow-mo?” And thankfully, I can almost immediately find out, with this high-speed camera, and that’s exactly what’s happened.

Before the world ended, I went swimming, and I saw that my Apple Watch had gone into Water Lock mode, which is where it sort of disables all the finger inputs from the screen because the water affects the capacitive screen and all that.

And to unlock it, you spin the digital crown, and it ejects all the water that’s inside it through the two speaker holes using the speaker itself, just sort of fires water all over your wrist. And I thought that’s brilliant, that’s genius, I wanna film that in slow-mo.

So why don’t we use our probe lens on our high-speed camera and see what that looks like? First things first, I will have to go for a swim. Water Lock. Okay, well that’s nice and wet, lovely. Put that under the light, let’s get the Phantom going.

Oh, I should’ve done that first. I’m using the probe lens because it’s macro will get me really close to the speaker holes, which are tiny. The downside is that it’s a maximum aperture of f/14, which is very dark, so I need a ton of light.

I figured I’d get a shot of the screen. This is 40 times slower, and you can actually see the refresh rate of the tiny OLED screen from top to bottom. This is now 80 times slower, 2000 frames a second.

I was immediately blown away at how much water actually came out in this shot. It’s mainly just because it’s macro to your eye. When you’re looking at it in real life, it doesn’t look like that much comes out.

After the initial burst, it actually looks like a lot of the water gets trapped. It’s trying to get out, but then gets sucked back in by the speaker retreating. So what it does, it stops, allowing the water to settle against the back of the speaker.

Starts again, which causes another burst of water to fly up. It does 10 full cycles of that. I think due to the sharp edge of the speaker hole, followed by the metallic surface that’s curved, it caused droplets to form around the speaker holes, which once big enough would just drip off.

I think if you were wearing the watch at this point, it would potentially just get pulled off onto your wrist. The surface tension of this droplet causes the smaller ones inside just to come out and join this one.

I should point out that the macro lens is making this look a lot bigger than it is, that’s actually a very tiny droplet there. The droplets were also able to climb upwards, which I thought was interesting.

Whichever droplet was closest to the lip, pulled the rest of the water out in that direction. And I saw here, as the droplet was getting bigger, it was starting to pull droplets back in that were trying to escape.



See that one almost made it out. And eventually after the droplet gets big enough, the small ones are able to catapult free. Once most of the water is out, you can get a much better look at the speaker surface, just rattling away back there.

Shooting a whole video in macro can sometimes cause you to lose the context and the scale of your subject, so this shot is just a reminder of how minuscule these little droplets are coming out. Really had to get right in there to see the speaker.

Just for a laugh, I wanted to see if it would work in reverse. So I dumped the watch underwater with air in the speaker, just to see if it would fire the bubbles out, and yes, it did. You can actually very clearly see the shock waves from the speaker because some of the bubbles that have escaped are still bobbing up and down to the same frequency as the speaker.

I actually found that a lot more interesting than I thought I would. To actually get to see the frequency that the watch uses to eject the water, and the fact that it then takes a break, gives it another go after it waits for the water to settle.

Very interesting way around having a watch that has a speaker and also needs to be water resistant. This is not an ad for Apple. I should probably say that, they didn’t sponsor this video. I don’t think I’ve ever seen Apple sponsor a YouTube video, it’d be very un-Apple of them, wouldn’t it? Hopefully you enjoyed that video.

Make sure you subscribe, and I’ll try and be back pretty soon with another little, how this works sort of video, ’cause I do enjoy making them. I’ll see you in the next one. Water Lock.

by