The following story shows the great effectiveness of the Rosary. Saint Louis de Montfort was planning to go to the island of Yeu, 17 km from La Rochelle, France, to preach a mission. It was during the War of Spanish Succession and English pirates roamed the seas, making the coast dangerous.
Because of the risk, the missionary's companions urged him to abandon his plans. But the saint had no rest until he had persuaded a few courageous sailors to take them along. The boat set sail and all went well until, three hours into the voyage, two pirate sailboats appeared on the horizon, bearing down on the missionaries and their boat.
The crew shouted in fear. The desperate sailors cried out, “We're lost!" Montfort's companions burst into tears. As for Montfort, he maintained his good spirits and began to sing hymns. He invited the others to join in, but they remained as mute as fish. Since you don't want to sing,” Montfort said, ”recite the Rosary with me!"
So they all got down on their knees, and sounding like frightened children, they recited Hail Marys that soared over the waters and penetrated the heavens. The Rosary over, the missionary spoke again: “Don't be afraid, Our Mother the Blessed Virgin has heard us! We are out of danger!” - “Out of danger?" the crew shouted, "Can't you see that we're now within firing range?" - “Have faith!" Montfort insisted.
Just then, a powerful gust of wind came up. The enemy ships turned around and, tossed about like walnut shells, disappeared over the horizon. The crew of the longboat were saved and landed on the island to the chanting of the Magnificat. When the poor fishermen heard of the miracle, they were all eager for the missionary's preaching. They all went to confession and, except for the governor, became fervent Christians, remaining faithful to the Rosary.
Kleine Lebensbilder by Michael Faltz; translated by Brother Albert Pfleger for Recueil maria.