If the object has an irregular shape, the volume can be measured using a displacement can. The displacement can is filled with water above a narrow spout and allowed to drain until the water is level with the tap. As the irregular object is lowered into the displacement can, the water level rises.
lets say we have a big lake with a lot of animals and you want to move the water to somewhere else. A lot of animals and fish, frogs will have to find a new home!