168 converted from July to October 1940. Data as for Pz Kpfw III Ausf F (3.7cm) and (5cm), Pz Kpfw III Ausf G and Ausf H, and gr Pz Bef Wg.
The Tauchpanzer was developed in mid-1940 for the proposed invasion of England (Sea Lion). The Pz Kpfw III were modified and provided with a submersion kit. Air-intakes were fitted with locking covers, and the exhaust was fitted with non-return valves. The cupola, gun mantlet and hull MG were sealed with waterproof fabric covers. An inflatable rubber tube surrounded the turret ring. While submerged, the tank drew air through a pipe from a float carrying a snorkel device and radio antenna which remained on the surface. A gyro-compass was used for underwater navigation. The Tauchpanzer could operate in depths of up to 15 metres. A vessel with a hinged ramp was used to disembark the Tauchpanzer at a suitable distance from the shore. With the cancellation of 'Sea Lion', the Tauchpanzer were no longer required in quite the same form. At Milowitz near Prague, in the spring of 1941, most of the tanks were modified to make them suitable for river crossing, with a fixed snorkel pipe attached through the commander's cupola.
From July 1940, four sections of volunteers from existing Panzer regiments were trained on the Island of Sylt, and the Tauchpanzer were to be ready for operations at Putlos by 10 August. In mid-October, three of these sections were attached to the 18th Panzer Division, and the remainder went to the 6th Panzer Regiment of the 3rd Panzer Division. On 22 June 1941, the Tauchpanzer of the 18th Panzer Division crossed the River Bug at Patulin.
During September and October 1940 volunteers of the 2nd Tank Regiment in Putlos were formed into Tank Battalion A and trained for Operation Sea Lion, the invasion of Great Britain. Two other special formations, Tank Battalions Band C, were being raised at the same time and the same place. These units later formed the 18th Tank Regiment of the 18th Panzer Division and adapted the Pz Kpfw III and IV for submerged wading. The following measures were taken. All openings, vision slits, flaps, etc, were made watertight with sealing compounds and cable tar, the turret entry ports were bolted from the inside and air intake openings for the engine completely closed. A rubber cover sheet was fixed over the mantlet, the commander's cupola and the bow machine gun. An ignition wire blew off the covering sheet upon surfacing and left the vehicle ready for action. Between the hull and the turret there was a rubber sealing ring which, when inflated, prevented the water from entering. The fresh air supply was maintained by a wire-bound rubber trunk with a diameter at about 20 cm, 18 metres long. To one end of this tube was fitted a buoy with attached antennae. The exhaust pipes were fitted with high-pressure non-return relief valves. When travelling submerged sea water was used to cool the engine and seepage was removed by a bilge pump. The maximum diving depth was 15 metres. Three metres of the air tube's 18 metre length was available as a safety measure. These submersible tanks were to be launched from barges or lighters. They slid into the water down an elongated ramp made of channel plates. Directing was achieved by radio orders from a command vessel to the submerged vehicle. Underwater navigation was carried out by means of a gyro compass and the crew was equipped with escape apparatus. The submerged machines were relatively easy to steer as buoyancy lightened them. After Operation Sea Lion was abandoned these vehicles were eventually used operationally during the Russian campaign in 1941 for the crossing of the River Bug.