We set it up on the inside of the top of the dodger, pointing at the top of the sliding hatch (only about 2 ~ 3 feet away, with just a small bit extending past the hatch slider. It will only go off if some one moves close to the top of the sliding hatch. I have set it to face the cockpit floor, very close to the main cabin doors, and have not had a problem there. You just need to play around with it to find the proper spot for your boat and level of comfort.

Greg