Lights are essential if you're ever out on a boat after the sun goes down. Sure, you have flashlights aboard. But what if you need one in a hurry and someone's misplaced it? Worse, what if the batteries are shot once you find it? Install a flashlight app, and whenever you have your iPhone, you'll also have a good flashlight -- as long as you don't misplace it. Among several free apps available, one of the best is myLite Flashlight and Strobe. It provides a strong LED beam as well as a variety of lighting effects on the screen. One of those special effects is an SOS signal, just in case you ever need it.
And just in case you ever sail into a dockside rock concert, the rock concert effect looks like a flaming cigarette lighter for you to raise.
But lights aren't all you need on that boat. Read on for more useful apps.