 However, this procedure is weather dependent and is therefore not reliable as a standalone measure.Captain Ernst A. Lehmann described how during World War I Zeppelins could temporarily remain at the sea surface by loading ballast water into tanks in the gondolas.In 1921 the airships LZ 120 "Bodensee" and LZ 121 "Nordstern" tested the possibility on Lake Constance to use lake water to create ballast.