Having both hands free, and the light where you're looking is the ultimate in usability.

For a strong beam I modified a Dorcy 41-1035 Xenon Rechargeable Lantern spotlight by replacing the bulb with a GE sealed beam bulb (pictured below). It's an exact fit, and makes for a lightweight and powerful focused beam that can light up a buoy well over a mile away (or light up your sails). For the bulb search for GE H7550-1 6V 8W Hand Lantern Sealed Beam Lamp