Measuring 3.3 by 7.3 by 1.6 inches (HWD) and weighing in at half a pound, the BackFloat is quite portable. Its black rubber, ruggedized contour has blue and metallic accents, with controls for Power, Volume (which works independently of, not together with, your device's volume), and Bluetooth pairing across its top panel, as well as a microphone for taking calls. One slightly odd quirk: You hold down the Bluetooth button to Answer/End calls, and this is also the button you press for Play/Pause—it's normal for Play/Pause and Call Answering/Ending to all use the same button, but less normal for that button to also be the Bluetooth pairing control.
The front panel, which points upward if the speaker is floating, houses two drivers and a passive bass radiator. (The speaker can also rest on a tabletop with the front facing forward, not up.) The BackFloat has an IPX6 rating, meaning it's both splash-resistant and shock-resistant—so it can float in water and get wet, as it's designed to, but you might not want to completely immerse it for very long.
A side port houses the micro USB charging connection (a cable is included, but it is quite short), as well as a 3.5mm Aux output that can be used for headphones or to send audio to another speaker.
The BackFloat automatically powers off after 60 minutes of not being used. That's a little bit longer than seems necessary, but it's better than no auto-off function at all. Monster estimates the battery life at roughly 7 hours on a full charge.
A very nice protective pouch is included—it has perforations for the sound to escape without things sounding muffled, and it's very well padded.
On tracks with powerful sub-bass content, like The Knife's "Silent Shout," the BackFloat does a laudable job of conveying a sense of deep low end. The bass isn't overwhelmingly powerful, but you wouldn't expect a speaker this size to sound like a subwoofer—and for what it is, the BackFloat produces an impressive amount of low-end. If you raise the speaker's volume to maximum and do the same on your sound source (we used an iPhone 5s, which paired quickly and easily), you're likely to get some distortion on tracks like this, but dialing back the levels a tad on either your mobile device or the speaker should solve the problem. For its size, the BackFloat gets quite loud.
Bill Callahan's "Drover," a track that lacks booming low-end, sounds balanced and clear through the BackFloat. His vocals get enough treble edge in the high-mids and highs to remain clear and in the forefront of the mix, but the low-mids also highlight the richness of his baritone delivery. The drums on this track also receive a nice rich low-mid presence—nothing about their bass presence is overly boosted or unnatural, but they do pack a bit more punch than you'd expect.
On Jay-Z and Kanye West's "No Church in the Wild," the kick drum loop's attack receives plenty of high-mid presence, which allows it to stay sharp and slice through the mix. The low-mid sustain of the loop sounds beefed up—and feels that way too, as the BackFloat gives off some healthy vibrations when its volume is pumped up. The sub-bass synth hits on this track are more implied than delivered, but you still get a decent sense of their low-frequency presence, and the vocals float cleanly over the entire mix.
Orchestral tracks, like the opening scene in John Adams' The Gospel According to the Other Mary, are delivered crisply and brightly, with a subtle added richness to the lows and low-mids. This means that lower register instrumentation does stand out a bit at times, but mainly it's the high-register strings, brass, and vocals that command our attention.
It's hard to complain too much about a water-resistant speaker that also delivers quality audio performance for its size, but the BackFloat does seem slightly overpriced. It delivers audio more or less comparable with speakers that cost significantly less, like the and the . True, they don't float in the water, but being water-resistant is a quality several lower-priced speakers also share—the and the are two solid examples.