In the 16th century, England was rather small and not particularly powerful. So why did King Philip II of Spain amass an armada and try to take it over in 1588? In 1554, King Philip married Mary Tudor, the Catholic Queen of England. The main goal was to keep England Catholic by producing a Catholic heir to the British throne. When Mary died childless, her Protestant sister Elizabeth claimed the throne.
With permission from the Pope in Rome, Philip amassed a fleet of war ships with the intention of using it to force England to remain Catholic by naming his daughter Isabella as queen. By Spanish historical accounts, Philip had built his Spanish Armada to over 130 ships and over 30,000 men, making it the largest naval fleet of its age. (So, yes, the Spanish Armada was large.)
Philip put the armada under the command of the Marquis of Santa Cruz. But the Marquis died, and the Duke of Medina Sedonia took over. The Duke was an accomplished and experienced warrior . . . but only on land. He had no naval experience whatsoever. This didn't worry Philip, who believed that he was doing the work of God and would therefore be victorious. Besides, the fleet was intended to be more of a troop transport than a naval force. The plan was to cross the English Channel and deposit the ground troops who would do most of the fighting. And the Spanish were regarded as the best ground soldiers in Europe. (So, no, the crews of the Spanish Armada did not have notable sailing skills.)
On July 29, 1588, the British and Spanish fleets met in battle. The Spanish outnumbered the British, but the British had the advantage in artillery and maneuverability. The Spanish lost that battle, but not horribly so. Because the British fleet blocked the English Channel, the only route back to Spain was north, around the tip of Scotland, and then down the coast of Ireland.
That's when English weather stepped in. A series of storms scattered the Spanish ships and brought heavy losses. By the time the Spanish Armada reached Spain, it had lost half its ships and three-quarters of its men. Thus, the Spanish Armada fell, and England remained Protestant.