At sea, people typically dehydrate from the lack of drinking water. Reverse osmosis makes it possible to desalinate sea water and produce drinkable fresh water. The bucket contains a membrane, through which water passes under pressure. When the pressure exceeds osmotic pressure, the direction of natural filtration will be reversed.
To achieve this effect, the bucket is designed to sink when placed in the sea. Beyond a certain depth, the weight of the seawater creates adequate pressure to push through the membrane, resulting in desalination and creating drinking water.