Scurvy was a major problem in long sea voyages prior to the late 18th Century when the preservation of fresh fruit was not possible. It was not uncommon for losses to scurvy on ships to outnumber crew members killed in enemy action - Commodore George Anson took six ships and 2000 crew to the Pacific Ocean in his circumnavigation of the world in the 1740s, and lost five of the ships and two thirds of his men.
James Cook is often credited as being the first sea captain to eliminate scurvy in his sailors, principally by using sauerkraut (pickled cabbage), although some people believe his success in doing this has been overstated not least because the vitamin C content of sauerkraut is minimal. Whatever the reason, in Cook's first voyage in the "Endeavour" between August 1768 and July 1771 there was not one case of scurvy. George Vancouver, an officer in Cook's second and third voyages, therefore instilled with Cook's insistence on a good diet, was later to spend the bulk of four years leading an expedition at sea without a major outbreak of the disease.
Lack of vitamin C causes scurvy because ascorbic acid provides a hydroxyl group for the hydroxylation of proline residues to from hydroxyproline in the protein collagen. These hydroxyproline residues form hydrogen bonds between chains of collagen, holding them together. Thus in the absence of vitamin C, the collagen chains fall apart, which leads to the weakened connective tissue which causes the scurvy symptoms.
Scurvy can be easily identified by the early symptoms  like
- Spots on the body
- No formation of new bones.
- The skin becomes pale
- The capillaries become weak
Other symptoms like Exhaustion, diarrhea, fainting, kidney or lung disease follow suit.
One of the more likely derivations of the American slang description of the British as "limeys" is the British habit of carrying limes on their ships as a defence against scurvy.