Yup! I agree with the above posts. The water level will appear to drop slightly. I find using hypothetical numbers can help.
Here's some I made earlier:
Boat: weight = 500kg
Anchor: weight = 6kg, volume = 1000cm3
Water: 1kg = 1000cm3 (not made up)
The weight of the boat will displace an equal amount of water. So the boat with the anchor on board will displace 506kg of water. When the anchor is thrown into the water, and isn't being supported by the boat any more, the boat will only displace 500kg of water.
However, the
volume of the anchor will displace some water now. 1000cm3 of anchor in; 1000cm3 of a water rise. (Not much in a small pond, but the displacement of a boat in a body of water it has any busines in being in, will be negligible anyway.)
So the overall drop in my little experiment is by 5000cm3. Basically, it's the difference between the density of the anchor and the density of water.
Of course, the anchor doesn't have a chain in my little world, and I hope to god we're not talking about salt water!!!!!
