Horatio Hornblower: The Fire Ship (1998) on Netflix

It's late in the 18th century, and acting Lieutenant Horatio Hornblower is serving on board the HMS Indefatigable, part of the British fleet at Gibraltar. Spain and France are allied against Britain, and Spain is intercepting and sinking most supply ships. His ship is sent to Oran, in Algeria, to buy supplies. While ashore, it is discovered that plague is rampant in the town. Quarantined on a smaller ship for two weeks with his crew and a diplomat, Hornblower uses the time to study for his upcoming lieutenant's examination. None of his crew is stricken with the dreaded disease, and they rejoin their ship just in time for the exam. During the actual oral exam, a Spanish "fire ship" (a ship ablaze sent into the midst of the fleet to burn it), is spotted and it's up to Hornblower and one of his chief examiners to save the fleet. This bravery more than proves Hornblower's ability to take on the duties of a lieutenant.