Construction of the first prototype began in February 1944 and was completed in less than 6 weeks.[4] The initial prototype, officially titled Bunteboot (but better known as Adam), was heavily influenced by the British Welman submarine.[4] It differed from the final design in a number of respects such as being nearly 2 meters shorter.[4] Following testing on the Trave river on 29 May twenty four Bibers were ordered.[4]