I would say that it fulfills its role: allow listening to music (I personally downloaded radio shows) swimming, which helps prevent boredom and swim longer without focusing on the number of laps completed! It is extremely easy to use, attaches easily, loads fast.
However, it should not be a purist sound! The sound sometimes changes depending on whether a head above or under water, which is not very pleasant. And above all, there is an imperative: the headphones can never be wet, otherwise it completely loses the sound after a swim! It is therefore very important to ensure that no water enters the ears. For that, I use a cap down as much as possible on the ears; I opted for the most suitable to my ear canal earphones (Walkman comes with three sets of earbuds of different sizes - for me, it's the smaller); and every 4-5 lengths, I réenfonce some headphones in the ears and I descend the cap.
With these small precautions, I am delighted, I can swim up to 1:30 in a row without worry. I have had no problems with the device (purchased through Amazon). I recommend it to all who love to swim but a little bored accumulating lengths ...
