Best of all, this company really stands behind their products. I had trouble with my headphones after about a month and sent an email, assuming it was a lost cause. Not only did I get an immediate reply, but they shipped replacement headphones out immediately. I can't compliment H2O enough for making me feel like a valued customer!
Be sure and register your products online when you receive them.

these are the best headphones I've tried of three types.  once you put them in and start swimming, do not remove an earbud or you'll lose the tight seal in the air and the sound quality will diminish.  if you put them in, keep them in, they're great.

sound quality was good

It has been a challenge to find the right size earpiece, but I think I've got it down now.  Trying to keep water out of my ears keeps the sound clear and even.  I swim in a pool with goggles and hold the housing in the back of my 1-piece bathing suit.  Today I tried on my neoprene hood that I use when I scuba dive, and it worked very well to hold the plugs in, keep the hair out of my face, etc.  IT WAS AWESOME!  My workout was finished before I got bored and bailed.

Good sound and good fit

First headset lasted about 6 months, being used about 2x per week.  Then it went bad, and I sent it back to the vendor for repair/replacement.   In the meanwhile, I ordered another one as a backup.  It was defective upon receipt, and only produced sound on one side.  I've tried a couple other brands as well, but haven't found anything that's reliable for long.