Bring your music on the water this coming summer by building your own floating speaker. All you need is a plastic container with a wide mouth (in this case a ketchup or coffee container), and MP3 player and some compact speakers.
Granted, you will have to be willing to take those speakers apart—so I wouldn't use anything expensive here. Still, it seems to be a pretty simple project that results in a usable waterproof speaker. Check out the instructable for the full DIY directions. [Instructables via Lifehacker]