A man rowing a boat in a lake throws his anchor into the water
Does the water level rise or fall?
Assuming the anchor sinks, the water level will fall
Whilst the anchor is in the boat, it displaces the volume of water equal to the weight of the anchor
When thrown in the water, it displaces less volume of water (since the mass of the anchor is greater than the equivalent size of mass of water)
Less water displaced means the water level falls