I have an older pair of Sony mp3 ones that I’ve grown not to like. My wife and I share a pair of these
https://shokz.com/products/openswim now. It’s easy to shuffle past her music to mine, and getting the purchased mp3s on there isn’t too hard. It does suck being limited to purchase mp3s, but I’ve not seen great reviews of any of the underwater specific systems (Bluetooth does not work-you Need a water specific transmitter/receiver system), or the ones that allow time expiring Spotify playlists. People talk about this all the time on triathlon forums.
I wouldn’t be able to get in my swim workouts without the music. With music, I’m good to be in there for 3000-4000 meters.