Attack of the Turtle by Drew Carlson
It's 1776, and the Revolutionary War is raging. Fourteen-year-old Nathan Wade is a patriot, but he's too young to join the fight. Then his cousin David Bushnell comes to town with a secret. David has designed a water machine that can explode bombs underwater. And his mission is to launch it against the British warships in New York harbor.
Based on actual historical events, this adventure story captures the drama of the first submarine used in naval warfare and the struggles of a teenager overcoming self-doubt.
Drew Carlson is a former magazine columnist, newspaper reporter, corporate writer, and editor.