If you need a waterproof wireless speaker, you need the $59.95 UWaterX3 Bluetooth Wireless Action Speaker. It's a small waterproof (up to 10 feet) Bluetooth speaker that generates reasonably impressive sound.
The UWaterX3 — which looks like a truck tire — is capable of delivering 85dB from its 50mm driver and directional sub-woofer. It's small enough to store in a backpack, gym bag or laptop bag. The rechargeable lithium-ion battery will hold a charge for up to 14 hours of music and features a low-battery indicator.
"But wait," you say, "I don't need a waterproof speaker?" Don't discount the UWaterX3 for that reason. It's also designed to withstand rain, mud, dirt, snow, shock and impact. So far it's handled many days' worth of unusually harsh winter weather here in Nashville, TN. Plus, it comes with multiple mounts for a bike, carabiner, pedestal and floater.
While it's not indestructible, the UWaterX3 is one of the toughest speakers I've run across.