Ferdinand Porsche
Ferdinand Porsche saw the potential of an amphibious version of the VW Kübelwagen (type82). The German Army was searching for a vehicle which could perform in difficult conditions such as snow, sand, mud. He combined these qualities and added all-wheel drive which had been developed at about the same time for the VW (type87).
First Trials   
The development project was called the type 128 which appeared in 1940. Thirty examples were built in 1941 at the Wolfsburg Volkswagen Works and delivered to the Army's Engineer units. The type 128 had a boat-shaped body. The army was very impressed. In 1941 Porsche received instructions for further development of the type 128. The type 138 was a type 128 but then with a little modified body it seems (version type 128 B). Some 100 more vehicles of this type were ordered. Another special version was produced type 129, probably a complete closed vehicle which could deliver bombs without a driver. This type was however not a success.
By the end of September 1940 the prototypes were tested in the lake called Max-Eyth near Stuttgart. You can select 2 or 4 wheel driving in the type 128. The car had a gearbox with 4 gears and with 2 sperrdifferentials and a powertransmission to the front wheels. Professor Porsche thought that the type 128 was too large and so unstable. Porsche started to create a smaller Schwimmwagen, which resulted in the project: type 166. The first 125 vehicles were produced by the Porsche Team and they were hand-made in Stuttgart. These cars are also known as "Vorserienschwimmwagen" or preseries Schwimmers. 
Type 166
The type 166 entered large-scale production in Wolfsburg (or "Stadt des KdF-Wagens", City of the Strenght Trough Joy Car). The production model, this is the "VW-Schwimmwagen" we know today, possessed a wheelbase which was 40 cm shorter than the earlier type 128. Also the vehicle's width had been reduced by 10cm. There were some small body modifications done as a result of the army-tests. The tow hooks for example got reinforcements. Now it was powered by the same 1131-cm3 engine installed in the Kubelwagen from 1943. In the water the engine drove a three-bladed propeller at the rear of the Schwimmwagen.
The type 166 was very popular, mainly because of the off-road capabilities thanks to the 4wheel drive. However, its amphibious capability was rarely used in action. It is difficult to confirm but it is said that in World War 2 the Schwimmwagen had lifespan of only 6 weeks. The production stopped in 1944, because of the large number of man-hours involved in the production and the high material usage. In 1945 and 1946, the British built six Schwimmwagens using spareparts that were left at the factory.
It is supposed there about 15.000 Schwimmwagens were built. After the war the Schwimmwagen was used by the local Police, firebrigades and mostly by farmers. Some people even cut doors in the tub in order to obtain an easy entrance to the vehicle. However, soon the vehicles were replaced by new ones so the schwimmwagen disappeared to the demolition firm....