This is what's inside a turtle shell. | Insider Science

The first submersible, a pioneering feat in underwater exploration, was the Turtle, designed by American inventor David Bushnell in 1775 during the Revolutionary War. This one-man, wooden vessel, resembling a barrel with a propeller and rudder, was the first submarine used in combat. Operated by hand-cranked propellers, it relied on human power for movement and submerged by flooding a small compartment, resurfacing via hand-pumped water expulsion. Its purpose was to attach explosive devices to B