Brightness is certainly a factor in choosing a spotlight, but brightness should not be your only consideration. You'll want a durable, long-lasting light, and the quality of construction is a major factor in the reliability of a spotlight. Look for booted switches, stainless steel hardware, rubberizing to minimize shock and vibration, and waterproof, or at least water-resistant, construction.

Ergonomics, the comfort and ease of handling, also plays a role. In any emergency, the ease of one-handed operation may be important. Pistol grips are generally the easiest to use—some lights are much more comfortable to hold for extended periods than others.

When using a spotlight, remember that the human eye requires from 12-40 minutes to fully recover its night vision after exposure to bright light. When using a spotlight on the water, point the beam down low, or in front of or behind another boat, or even up into the rigging. Avoid directing your beam in anyone's eyes—you don't want to destroy the night vision of another boater trying to operate safely in the same area as you.