Horatio Tremblis invented the water rocket accidentally on the starry 4th of July evening of 1877. After failing at his previous two jobs (a paper engineer and a rodeo clown), he decided to take up pyrotechnics. In the past five years, he had been attempting to invent a new type of firework--one that would be shot down into a body of water and explode at a depth of about 15 ft. Success came when he accidentally poured the remnants of a can of Planter's Honey Roasted Peanuts into an open firework. He sealed it off, unknowing of the sweet and salty goodness locked inside. He lit the device off of his 6-ft dinghy in the middle of the Caspian Sea. The vessel capsized as the rocket plunged into the water.
A week later, Horatio's body washed up on shore, impaled with, and burnt by, the world's first Water Rocket.
See Webster deffinition #2