Ultimate Ears Boom 4

A step up in size that still floats. UE rates the Boom 4 as IP67, floatable and drop-proof, so it can ride along on a raft or sit at the edge of a lake swim without anyone guarding it, and it is loud enough to cover a small group around a fire ring. Rated battery is 15 hours, enough for a full day and an evening. PartyUp links it with more than 150 other UE speakers if friends bring their own. Its list price is $149.99, and it does go on sale, which makes it one of the better values among the mid-size picks when it does.