text: Well basically in osmosis, there are 3 solutions: hypertonic,hypotonic and isotonic. Drinking saltwater causes a hypertonic solution in your cells. The most basic way to explain this is as you drink saltwater, the salt solutions gather outside your cells. No water comes in and the remaining water gets pushed out causing crenation, shriveling of the cell. You can see it externally when your hands wrinkle when wet for too long right? Imagine it acting through your internal organs so I think its kinda like dehydration from within, which is exactly what people try to avoid  when they drink saltwater out of desperation right? hehe.