The Mk 58 Mod 1 marine location marker (fig. 4-9) is designed for day or night use in any condition calling for long-burning, smoke and flame reference-point marking on the ocean's surface. In addition to being used for antisubmarine warfare, it is used for search-and-rescue operations, man-overboard markings, and as a target for practice bombing at sea. The marker produces a yellow flame and white smoke for a minimum of 40 minutes and amaximum of 60 minutes. It is visible for at least 3 miles under normal operating conditions. 

The Mk 58 Mod 1 marine location marker consists of a cylindrical tin can approximately 21.78 inches long and 5.03 inches in diameter. The can contains two pyrotechnic candles of a red phosphorus composition. The ignition end of the marker has three holes—two for smoke and flame emission and one for water to enter the Mk 72 Mod 1 seawater-activated battery. Adhesive foil disks hermetically seal the two emission holes. A reinforced adhesive foil strip with a rectangular pull ring hermetically seals the battery cavity hole. The adhesive foil seals are protected during handling and shipping by a replaceable polyethylene protective cover. 

Launching Methods 

The Mk 58 Mod 1 marker may be hand launched, externally launched from suitable aircraft bomb racks by using breakaway suspension bands, or launched from sonobuoy launchers by using a sonobuoy launcher container (SLC) and the appropriate foam spacer. No matter howthe marker is launched, the protective cover, the pull ring, and reinforced adhesive foil strip over the battery’s cavity is removed. When launching the marker from a sonobuoy launcher, you remove the protective cover and pull ring and reinforced adhesive foil strip. Then, load the marker onto the bomb rack. After securing the marker to the bomb rack, attach the pull ring to an arming wire, which is attached to the bomb rack. When the marker is released from the bomb rack, the arming wire retains the pull ring and removes the foil strip covering the battery's cavity. When submerged, the Mk 72 Mod 1 battery is activated by seawater. Current from the battery initiates a Mk 13 electric squib, which ignites the starter composition of the first pyrotechnic candle. The composition  ignites the starter pellet, which, in turn, ignites the first candle. When the first candle is nearly burned out, its heat ignites the transfer time fuze, which carries ignition to the second candle starter composition. This starter composition initiates the second pyrotechnic candle.