The First Submarine
Cornelius van Drebbel, a Dutch inventor, managed to build a submarine in 1620. He wrapped a wooden rowboat tightly in waterproofed leather and had air tubes with floats to the surface to provide oxygen. Of course, there were no engines yet, so the oars went through the hull at leather gaskets. He took the first trip with 12 oarsmen in the Thames River, staying submerged for 3 hours.