Price reduced to $79 now, June 6th, original deal below:
A bit of a niche product but a properly waterproof Bluetooth speaker built for the marine environment, RRP was $319.99, though I have seen them down at $150 on special before. Club membership required to get the deal, though that is free. Could add something cheap for free P&P as the threshold level is over $99.
"Introducing the FUSION STEREOACTIVE, the world's first purpose built watersport stereo, available in this white and black style. Designed and engineered in New Zealand by FUSION. The STEREOACTIVE is designed for the challenge of life on the water and tuned to deliver crystal clear audio that enhances any activity. This isn't your standard Bluetooth speaker, this is a fully waterproof portable watersport stereo. Featuring a unique Puck mount system that lets you attach the stereo to any paddle board, kayak, canoe, dinghy/tinny/jon boat or even Jacuzzi.
IPX7 Waterproof Rating