It's in podcast form, as well. I just searched for the name of the book in Pocket Casts and the author is listed as Loyal Books. Going to give it a try on my walk today. Thank you!
They're called "SYRYN Swimbuds Flip and Waterproof MP3 Player". Just got them a few years ago as a quick, inexpensive Amazon purchase. Looks like they're a bit more expensive nowadays, but not too bad.
They work fine-- only ones I've ever had, so I have nothing to compare them to. I can confirm they've survived over 200 hours of lap swim, though.
I listened to it while swimming laps. The readers have great, rhythmic pacing.