This publication relates to a system and a method for supply of water in a seafood farm, wherein a seafood tank (11) is supplied with water from a water source (12). The system comprises: - a chamber (13),- a displacing body (15) adapted to be lowered into and raised out of the chamber (13),- an inlet (14) with valve (20) connecting the chamber (13) to the water source (12), controlling the inlet flow of water, the valve (20) being a one way valve； and - a chamber outlet (19) connecting the chamber (13) to the seafood cage (11). The method comprises comprising at least the steps of: opening an inlet valve (20) of the chamber (13)； filling the chamber (13) with water, preferably to a same water level as the water source (12)； shutting the inlet valve (20) of the chamber (13)； lowering the displacing body (15) into the chamber (13)； directing a flow of displaced water through the chamber outlet (19)； and raising the displacing body (15) out of the chamber (13).
