Complex sentence: It was built in 1775 by American David Bushnell as a means of attaching explosive charges to ships in a harbor, for use against British Royal Navy vessels occupying North American harbors during the American Revolutionary War.
Split into simpler sentences: It was built in 1775 by American David Bushnell as a means of attaching explosive charges to ships in a harbor. Bushnell designed her for use against British Royal Navy vessels occupying North American harbors during the American Revolutionary War.