He also built the first navigable submarine in 1620 while working for the English Royal Navy. He manufactured a steerable submarine with a leather-covered wooden frame. Between 1620 and 1624 Drebbel successfully built and tested two more submarines, each one bigger than the last. The final (third) model had 6 oars and could carry 16 passengers. This model was demonstrated to King James I in person and several thousand Londoners. The submarine stayed submerged for three hours and could travel from Westminster to Greenwich and back, cruising at a depth between 12 and 15 feet (4 to 5 metres). Drebbel even took King James in this submarine on a test dive beneath the Thames, making King James I the first monarch to travel underwater. This submarine was tested many times in the Thames, but it couldn't attract enough enthusiasm from the Admiralty and was never used in combat. More recently it has been suggested that the contemporary accounts of the craft contained significant elements of exaggeration and it was at most a semi-submersible which was able to travel down the Thames by the force of the current. Cultural references Cornelis Drebbel has been honoured on postage stamps issued by the postal services of both Mali and the Netherlands in 2010. A portrayal of Cornelis Drebbel and his submarine can be briefly seen in the film The Four Musketeers (1974). A small leatherclad submersible surfaces off the coast of England, and the top opens clamshell-wise revealing Cornelis Drebbel and the Duke of Buckingham. Drebbel was honoured in an episode of the cartoon Sealab 2021 during a submarine rescue of workers on a research station in the Arctic. A German U-boat captain fired a pistol in celebration at the mention of Drebbel, to shouts of, "Sieg Heil! Cornelis Drebbel!" Also, on the Sealab 2021 Season 3 DVD, Cornelis Drebbel has two DVD commentaries devoted to the story of his life. In the Dutch Eighty Years' War comic Gilles de Geus, Drebbel is a supporting character to the warhero Gilles. He is drawn as a crazy inventor, similar to Q in the James Bond series. His submarine plays a role in the comic. Richard SantaColoma has speculated that the Voynich Manuscript may be connected to Drebbel, initially suggesting it was Drebbel's cipher notebook on microscopy and alchemy, and then later hypothesising it is a fictional "tie in" to Francis Bacon's utopian novel New