Eustace the Monk

Eustace the Monk, sometimes known as the Black Monk, was a younger son of a lesser noble family in Boulogne. As a young man he spent some time in a Benedictine monastery, hence the 'monk' part of his name. Given his period of activity, he was probably born in the late 12th century. Initially, he served the Count of Boulogne, but was eventually outlawed and turned to piracy.
He and those he attracted soon came to control the Straits of Dover. Like many early pirates he turned mercenary and sold the services of his squadrons to the highest bidder. From 1205-1212, he served King John of England in his war with Philip II of France. He raided the French coastline and seized the Channel Islands as a base of operations.
King John outlawed Eustace for indiscriminant pillaging of English subjects, but soon forgave the pirate, as his services were too important. He is said to have built a palace in London and sent his daughter to school with the noble girls or England.
Ever the mercenary, Eustace and several other French pirates switched sides in 1212. Serving the French he attacked Folkestone to avenge the English seizure of his Channel Island bases. During the English civil war that broke out in 1215, he lent aid to the rebels and helped to transport and protect the troops of Prince Louis of France when they invaded southern England. The war continued after King John died in 1216 and many of the rebels deserted over to the side of King Henry III. In 1217, while transporting additional troops Eustace and his ships met an English fleet. Using powdered lime the English blinded the French and boarded.
The battle ended with the English being victorious. Several French nobles were ransomed, but Eustace was beheaded on the spot.
While it is true that the forces of Eustace the Monk were maritime in nature, there was little similarity with the pirates of the Golden Age. At the time ships were little more than transport and floating battlefields/castles. The primary strategy was to maneuver to board the enemy's ships and fight it out in a general melee. Perhaps the biggest fault one sees in Eustace is his mercenary nature, but then if it weren't for that he would have been little more than a naval commander and not a pirate.