.Brightness : When it comes to underwater lights, the general rule is the brighter the better. This is particularly true in night diving, when a bright light with a wide beam, Beam angle : Depending on what kind of diving you do, a tight beam or a wide flood may each be appropriate. A tight bright spot is useful for spotting, for looking into crevices and under ledges, and a must for limited visibility diving in murky water. A tight beam with no spill will cut through the murkiness and allow you to see further, when a wide beamed light would reflect back from the particulate and make it more difficult for you to see. Tech divers tend to prefer narrow beam lights because they allow you to see further down long passages or into wrecks.