This marine head unit brought out by Alpine is ideal for boats.

It features a large 2-line LCD screen (viewable in direct sunlight), skip-resistant CD mechanism to ensure continuous playback while you’re on the waves, is fully IPx5 waterproof and salt fog/UV certified. Also has EEPROM no-loss memory, ensures even when the boat is not in use and the battery is disconnected, all your radio presets, zone controls, sound adjustments will stay intact.  It plays CD / iPod / iPhone (limited models), and can be expanded for Bluetooth, HD radio, Imprint, & SIRIUS XM with the purchase of additional adapters.