Why is ocean water not usable for drinking and crop irrigation?

The first guy does not know what she/he is talking about! When we need water our cells get big, then when we drink water its makes them small again.But, when you drink salt water it makes them bigger does to the salt.Making them bigger and thristier so you drink more making it BIGGER.But, if you drink fresh water it returns you to normal!(^_^)

- I don't know what "the first guy" said, but if it is the opposite of this, then he was right. Ocean water is very high in sodium. The role of your cells(as far as water) is to keep the concentration of solute in the cells the same as outside. In this case, salt is the solute. If you ingest too much salt, your cells will let out water to even out the concentration. This makes them SHRINK. When you drink too much fresh water, the concentration of solute inside your cells is higher, causing them to draw in water. This could eventually cause them to lyse, or burst, from having too much water in them.