Submarine snorkel - Wikipedia Until the advent of nuclear power, submarines were designed to operate on the surface most of the time and submerge only for evasion or for daylight attacks. Until the widespread use of radar after 1940, at night a submarine was safer on the surface than submerged, because sonar could detect boats underwater but was almost useless against a surface vessel. However, with continued radar improvement as the war progressed, submarines (notably, the German U-boats in the Battle of the Atlantic) were forced to spend more time underwater, running on electric motors that gave speeds of only a few knots and very limited range. Germany defeated the Netherlands in 1940; their capture of O-25 and O-26 was a stroke of luck for the German Navy, the Kriegsmarine. The Dutch O-21 class were equipped with a device named a snuiver (sniffer). The Royal Netherlands Navy had been experimenting as early as 1938 with a simple pipe system on the submarines O-19 and O-20 that enabled diesel propulsion at periscope depth, while also charging the batteries. The system was designed by the Dutchman Jan Jacob Wichers. The Kriegsmarine first viewed the snorkel as a means to take fresh air into the boats but saw no need to run the diesel engines under water. However, by 1943 more U-boats were being lost, so the snorkel was retrofitted to the VIIC and IXC classes and designed into the new XXI and XXIII types. The first Kriegsmarine boat to be fitted with a snorkel was U-58, which experimented with the equipment in the Baltic Sea during the summer of 1943. Operational use began in early 1944, and by June 1944 about half of the boats stationed in the French bases had snorkels fitted. On Type VII U-boats the snorkel folded forward and was stored in a recess on the port side of the hull, while on the IX Types the recess was on the starboard side. The XXI and XXIII types both had telescopic masts that rose vertically through the conning tower close to the periscope.