The red dot sights are GREAT for quick, close in work. They have a wide angle of view, and allow for both-eyes-open shooting. A dot or reticle is reflected onto your eye, representing a point out at optical infinity that is adjusted to match the strike of the round.
Not only do you not have to line up a front and rear sight (ghost ring rear sights are good iron sights for your purpose, too), you don't even need a good shooting position. As long as your eyeball can see the dot, the round will hit whater the dot is resting on, even if you are holding your weapon sideways.
That sounds pretty useful on a boat after all.
Well said, Winmag. Any brand names/models you'd recommend?