PURPOSE: To raise the light yield and simultaneously enable safe, stable-storage and simple structure by forming a tube containing a pyrotechnical charge by a material which does not burn away, and making the pyrotechnical charge as a specified composition consisting of sodium nitrate, polyolefin resin and magnesium.

CONSTITUTION: A sea marker is so constructed that a tube 1 is surrounded with a float 2, the lower part of the tube 1 is provided with a trimming weight 4 for keeping the sea marker in the vertical state, and a light charge 5 in the tube 1 is ignited through an intermediate base charge 7 arranged thereon. The tube 1 is formed of a material which does not burn away, such as steel, and the light charge 5 consists of 30-60 wt.% of sodium nitrate, 3-18 wt.% of polyolefin resin, and 30-60 wt.% of magnesium. Further, 40-80 wt.% of barium nitrate, 1-10 wt.% of sulfur, 1 to 10 wt.% of charcoal, and 1-5 wt.% of black powder are superposed on the light charge 5, and a primer 9 is arranged thereon.