The trouble with boats is, things get wet. That’s why you don’t want a regular automotive head unit for playing music out on the ocean or lake. What you need is a marine head unit. These are designed and built to withstand rain, fog, and salt spray, as well as sunshine and sudden temperature changes. (Those UV rays might feel good but they really beat up plastics and other materials not engineered for life outdoors.) Head units for outdoor applications take many forms. Most follow the rectangular DIN size format but others are squarer or even circular for a more interesting appearance. Like their automotive equivalents, marine stereos and head units come with a host of ways in which to play your collection of music. Some even offer Sirius XM satellite radio so you can follow news or sports while far offshore. Our guide to marine stereos and head units explains the various options and features to look for. Once armed with this information you’ll be able to make an informed buying decision. You probably already figured you need Bluetooth, but have you thought about screen brightness? When you’re using a stereos or head units in the open air you want to be able to see the screen. It’s not an issue with car systems, but it’s something marine equipment designers consider. Power is another area where marine stereos need particular consideration. Enjoying music against a background of engine noise and waves often means cranking up the volume, so you’ll probably be fitting a marine amplifier. If that’s the case, look closely at the outputs your marine stereo provides. Pre-amp outputs will save you from using speaker level amplifier inputs. Having ample reserves of power also helps if you want to expand your system in the future. And don’t forget, marine-grade stereos and head units aren’t just for boats. You should have one in your ATV, jet ski or off-roader. In fact, any place where it’s exposed to the elements.