This was a big experiment so let me know what you think... I filmed this with my macro lens and used a water dropper and spray bottle to melt the bath bomb. I also recorded just the sounds of the bath bomb by holding it up to my mics, so I layered that sound with the video.
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app