Your best bet is the surefire 6pn...that is...if it has to be surefire, but as a diver I can tell you that princeton tec, ikelite, as well as other makers offer cheaper, brighter lights for diving or deep water submersion. Those are made for diving...but surefire is more of a combat oriented light, that yes, will withstand the weather and elements, as well as shallow water, but not recommended for deeper water. I personally am going with the 6pn but they are about 90- 112 dollars