This is book 1 of the "Hornblower" series.

This note does not contain major spoilers for the book.

A collection of short stories dealing with Hornblower in his midshipman years, including a failed attempt to pass for Lieutenant.

I remember the classic story about the cargo of rice (in which rice's ability to absorb water conceals the fact that a prize is holed below the waterline until it's too late), and "The Even Chance" where Hornblower is so depressed he engineers a duel with a 50:50 chance of surviving as being better than his life as it was.