During World War II The German Navy deployed weather buoys ( Wetterfunkgerät See — WFS ) at fifteen fixed positions in the North Atlantic and Barents Sea . They was launched from U @-@ boats into a maximum depth of ocean of 1000 fathoms ( 1 @,@ 800 metres ) , limited by the length of the anchor cable . Overall height of the body was 10 @.@ 5 metres ( of which most was submerged ) , surmounted by a mast and extendible aerial of 9 metres . Data ( air and water temperature , atmospheric pressure and relative humidity ) was encoded and transmitted four times a day . When the batteries ( high voltage dried @-@ cells for the valves , and nickel @-@ iron for other power and to raise and lower the aerial mast ) was exhausted , after about eight to ten weeks , the unit self @-@ destructed .