What did Robert Fulton invent'?

Answer 1

I'm assuming you're talking about Robert Fulton, who did not actually invent, but played a key role in the invention of the steamboat. In 1804 he also tested the first successful submarine that he had built for the British navy.

Answer 2

John Fulton was interested in the recently-invented steam engine (by Joh Fitch), and thought it could be used to power ships.
He was instrumental in making steamboat travel a reality. This was his real invention next was his invention of the first submarine.

In 1804, Fulton tested the first successful submarine, which he had built for the British Navy.
To build an efficient, reliable steamboat, Fulton used a special English steam engine.
The ship's bottom was flat and its stern was square. Clermont made its debut on August 17, 1807,
steaming upriver from New York to Albany, and it soon entered into commercial service.
The hilly terrain of New York made water travel faster than land travel, and Fulton's boat
-- formerly known as "Fulton's Folly" -- was a hit. Within five years, Fulton would be running services
on six major rivers plus the Chesapeake Bay, and making very large profits.

Answer 3

how did robert fulton helped America to make life better