Sailors use desalinated water for just about everything. Desalination is the process which removes the salt and mineral content from ocean water, producing fresh water that is free from ion content. This is very important for drinking water, because if a human drinks ocean water, the bodys cells will become dehydrated by osmosis, which means the fresh water in them will diffuse out of them to equalize the salt in the water of the external environment. As far as cleaning, if you use ocean water that has not been desalinated, you will be spreading salt all over the surfaces you are trying to clean. When the water evaporates, a thin, white, salty residue will exist on every surface you cleaned. So just how clean did you leave it? Fresh water does not do this, as there is nothing dissolved in the water to leave behind.