H2O Audio Sonar 2 Pro Review: Bringing Music to Swim Training

When I was training for my first triathlon, every morning started with a several-hundred-yard swim in the pool at my gym. Staring at that black line at the bottom of the pool, lap after lap, my mind went numb. Then I got a waterproof iPod Shuffle from this new company called H2O Audio, and my boredom issue was solved. 

Ten years later, H2O Audio is still providing swimmers with audio, but now its focus is on headphones. The company’s latest waterproof bone conduction headphone, the Sonar 2 Pro ($150), is about half the size of its predecessor, stores up to 8 hours of music, and offers clear sound and solid bass underwater. 

In short: If swimming endless laps in a pool drives you mad with boredom, the H2O Audio Sonar 2 Pro could be the perfect solution. With excellent sound quality, a long battery life, and a secure hold on your goggles, these waterproof headphones deliver.

Compare the H2O Audio Sonar Pro 2 to the other bone conduction headphones we tested in our Best Bone Conduction Headphones Buyer’s Guide.

H2O Audio Sonar 2 Pro Review

Brand Background

H2O Audio started out as a company that would waterproof iPod Shuffles, Kindles, and resell them, as well as waterproof device cases that connected with wired headphones that work underwater. With the development of Bluetooth and wireless streaming, H2O Audio pivoted to focusing on better and better waterproof headphones that delivered quality audio underwater. 

How I Tested the H2O Audio Sonar 2 Pro  

I moved from swim training to powerlifting after my last swim event, which means I haven’t been in the pool much lately. So I recruited competitive swimmer and triathlete Sheri Christie to put the Sonar 2 Pro through its paces. 

Sheri swam three or four times a week, wearing the headphones and evaluating them based on sound quality, stability, comfort, and ease of use. She tried different strokes (freestyle, butterfly, etc.) to test the Sonar 2 Pro’s stability.

Key Features

First off, the Sonar 2 Pro is rated IPX8, which means you can swim with it without worry. It’s also a marked difference from the H2O Audio headphones we included in our Best Running Headphones buyers guide, the H2O Audio Tri 2 Pro ($200). The Tri 2 Pro’s over-the-ear design makes it ideal for not only swimming but dry land activities like running as well (I use them daily in my cold plunge).

The Sonar 2 Pro is designed to clip onto a swimmer’s goggles or to fit underneath a swim cap, so it’s made specifically for the pool. 

Through H2O Audio’s PLAYLIST+ feature, users can upload 8 hours of music, podcasts, or audiobooks, so you don’t need to be near your phone to use them. The bone-conduction audio delivery is clear and powerful, so you can hear the audio underwater.

It’s also just over half the size of the first Sonar for a more streamlined swim profile. The battery life has also been improved over the first iteration, with up to 10 hours of continuous play. 

The Good 

One of the biggest challenges with creating swimming headphones is delivering sound that is clear through the swooshes and gurgles that come with a swim workout. Sheri was happy to report that these headphones delivered that clear sound in spades. “The sound is so clear when underwater,” she said. “I actually had to turn down the volume because the bass hit so hard!” 

When I first unboxed the Sonar 2 Pro, I was skeptical that the small clips on the side would hold the headphones in place, but after a few swims, Sheri couldn’t knock them loose. “The headphones didn’t budge at all while flipping,” she said. “They also didn’t move when I swam with fins or did the butterfly stroke — they are solid.” 

Another potential concern I had was that the headphones would feel uncomfortable when tucked underneath the goggle straps or swim cap, but they weren’t noticeable at all during testing — the only thing you’ll notice is the music. 

The three-button controls are simple and intuitive. With a little bit of practice before getting into the pool, switching tracks, controlling the volume, and pausing the music were no problem. 

Overall, swimming with the H2O Audio Sonar 2 Pro was a hit with my tester. They felt extremely stable, the audio was crystal clear, and the controls were easy to use. Having music to listen to actually helped her drop her 100-yard pace during a 3,000-yard swim from 1:55 to 1:39. She’s already experimenting with music that will speed up her cadence. 

The Bad

The main issue that our tester had with the Sonar 2 Pro concerns uploading audio. Since Bluetooth doesn’t work well underwater, the PLAYLIST+ feature requires you to download H2O Audio’s app and manually upload the songs/podcasts/audiobooks. 

While this is a useful feature because it means you don’t need to have your phone near you when you swim, the process itself is fairly time-consuming. In a nutshell, you need to create a playlist in your music app, then play the entire playlist through so the headphones can record everything. Hopefully, there will be a drag-and-drop feature sometime in the future. 

Also, these headphones are basically two independent headphones connected with a flexible strap. This means you need something (like goggles) to clip them to in order to use them, so unless you clip them to a hat or headband, you’re not going to be able to run or cycle with them. If you want a pair of headphones that aren’t exclusively for swimming, check out the H2O Audio Tri 2 Pro.

H2O Audio Sonar 2 Pro: Final Thoughts

With a small profile, long battery life, and top-notch underwater sound, the H2O Audio Sonar 2 Pro ($150) is ideal for adding audio to your swim workouts. The headphones lock securely to your goggles regardless of what stroke you use, and the audio is top-tier (once you power through the arduous uploading process). 

Its goggle mounting system makes it work almost exclusively for swimming, so triathletes may want to go with something a little more versatile. But if you’re looking to alleviate the boredom of swimming endless laps in the pool or you want some extra motivation to hit some distance PRs, the H2O Audio Sonar 2 Pro is an excellent option.