Magellan led his ships through the deep and narrow strait w- hich is now named after him. During this difficult exercise in navigation , the captain and crew of the San Antonio managed what they had failed to do at San Julian - they slipped away and headed back to Spain. Undaunted, Magellan and his three r- emaining ships entered the ��Great South Sea��. He called his men together for a service of thanksgiving, and solemnly named it the Mar Pacifico (��Peaceful Sea��). Magellan reckoned it was now only a matter of days before t- he expedition reached the Philippines or Spice Islands. He ea- gerly plotted their westerly course across the blue Pacific, aided once more by the brisk trade winds. But, as day followe- d day, then week followed week, with no sight or sign of land, the crews became anxious and restive. Magellan himself reali- zed something was very wrong with his calculations. His ��sea�� was, in fact, the biggest ocean of all, covering a third of t- he total surface of the world. The voyage proved a terrible ordeal. In all that vast an- d empty ocean, they came upon just one tiny, uninhabited isla- nd. Stocks of food and water ran low. Worse still, as they sa- iled back into the tropics, what little food was left went ro- tten. The men ate anything they could find, rats, maggots, st- rips of leather, even sawdust. They began to suffer from scur- vy. Their skin broke out in sores, their limbs became horribl- y swollen, they grew so weak they could not stand or even rai- se an arm. One by one they died. When the expedition finally reached the Mariana Islands, so- me 2,000 kilometres ( 1,250 miles ) east of the Philippines, the survivors had crossed nearly 13,000 kilometres ( over 8,0- 00 miles ) of the Pacific Ocean.