Speaker Cleaner

It can help. The tone moves the speaker back and forth fast. That can shake droplets out of the grille and the gap in front of it. It can't reach water inside the phone, and it doesn't repair a damaged speaker. If the sound is still muffled after a few rounds and a few hours of drying, get the phone checked.

It's the frequency most water-eject tools use. It's low enough that the speaker cone moves a long way, and high enough that a small phone speaker can still play it. Much lower tones are below what a phone speaker can play.

No. At high frequencies the speaker cone moves much less, so it pushes less water. Most people can't hear 20,000 Hz, and many phones can't play it.

Don't play it through anything in or on your ears: it's loud. For wet AirPods or earbuds, shake out the water with the speaker facing down, wipe them, and let them dry in open air before charging. Apple Watch has its own Water Lock setting, which plays a similar sound.

Start with 60 seconds, speaker side down, and repeat two or three times if you still see or hear water. If it's still muffled after that, let the phone dry instead.

Yes. It runs in any current browser on Android or iPhone. Turn the media volume up, not only the ringer volume.