My sons belongs to a local squadron of Civil Air Patrol, when he geared up for a search and rescue, the Captain requested each Cadet to place two snap & glow sticks in their provision bags. This is a great idea for the fishing vest pocket. Reason being, they float and are completely water proof. The idea of two, is for the duration one might be wondering off course. Needless to say, they found the fisherman with a broken fibia 3 miles down stream of his vehicle because he thought he could swim to the next cabin before hypothermea took hold. Oddly enough, they found him at dark because of the glow stick he had packed the year before; for such an Emergency.