On the part of the Thames between the Tower of London and Greenwich, the Dutch scientist Cornelis Drebbel, inventor and engineer demonstrated his submarine. The trip took about 3 hours. One of the trips was probably done with King James. The boat was covered with greased leather and made waterproof. Rocks made the boat heavy so it stayed under water.
Some sources state that there were bottles of air under pressure to get fresh air. Other sources state there were two tubes to get air from the surface.