The SwiMP3 player is a waterproof MP3 player with 256MB internal memory. That's approximately 60 songs, and the player has a 10-hour lithium ion battery. The device charges via USB and can be synced with both Windows (98SE, 2000, ME, XP, Vista) and Mac-based PCs (OS 9, OS X, or higher), and it even works with iTunes. Supported audio formats include MP3 and WMA files. Here's a full list of technical information including iTunes and Windows Media setup.
According to FINIS, the SwiMP3 "attaches easily to any swim goggle or snorkeling mask. For audio playback it relies on bone conduction of sound. When the device is placed on any bones of the skull (the cheekbones or the mastoid tip), it leads to vibration of the fluid in the inner ear. Thus swimmers can enjoy clarity of sound with the SwiMP3 device that was never before possible. Bone conduction is a safe, well-established hearing mechanism in humans that the SwiMP3 player leverages to enhance aquatic activity. FINIS' application of the technology brings an entirely new level of experience to swimmers of all abilities."
To be able to listen to the Jaws theme or any music underwater would be pretty cool. But at $149.99, I think they may take a bite out of you before you get wet.