Osmosis revolves around water due to the osmotic gradients and pressures. It works in cells where water can pass through partially permeable membrane when there is a difference in solution concentration, so if a potato low salt concentration is put into salty water (therefore high salt concentration) this creates and osmosis gradient and the conditions under which osmosis can act, so the water will move from low concentration to high concentration to dilute it…..for example plants use osmosis to ‘drink’ so you could think of it this way, ‘osmosis sucks’ high concentrated solutions ‘suck water from low concentrations’.
The process of osmosis can be harmful to fish (e.g. fresh water and salt water) if placed in water of different salinity (saltiness) they will die, this is rapid in the case of the salt water fish. Hope this helps.