A not-so-famous technological innovation of the Revolutionary War was the world's first combat submarine.  Here it is:  The American Turtle!  (The screws are for drilling a hole in the target ship's hull, attaching a timed bomb, and disengaging.)

Its inventor, David Bushnell, was feverish the day of The Turtle's big debut, and so was his brother Ezra.  So a game volunteer, Ezra Lee, offered to take The Turtle out for a ride and see what he could blow up with it.  Unfortunately -- nothing (exploding an English ship would've been really useful right then, as England had a rather overwhelming navy sitting plump by New York City).  The Turtle had no visibility when submerged, and Lee seems to have tried to drill a hole in a rudder, whose material was too tough for the screw.

But it wasn't a dead loss, because when The Turtle surfaced on its melancholy return to base (it held enough air for only about thirty minutes of submersion), it really, really freaked the English out.  All the more so when they sent out some boats to check out what on earth was "bobbing with intent" on the water, and Lee released the bomb.  The English scurried back right quick, the bomb exploded, and England's ships cut their anchors and kept a wary distance for a wee while -- both tactically and strategically irrelevant, but fun!

The Turtle never got a chance for a second mission; it was scuttled during the Continental Army's flight, to keep it out of English hands.