What happens to the level of the water when you do this?

The water level will go down when you throw the body in. Try it in your sink. Fill your sink with water and float a bowl (boat) in it. Then, fill the bowl with silver wear (body and rocks) or anything more dense than water. Mark where the water level is on the side of the sink. Now, take the silver wear out, and put it in the water so it falls to the bottom of the sink. You will notice that the water level went down. When the silver was in the bowl, it displaced much more water than when it was at the bottom of the sink. Therefore, the body will displace more water when it is inside the boat than when it falls into the water.

well actually that depends on the time you measure. The water leverl rises (I think not measurable, but it does) when u, the body and the boat go in the water. but of course it'll go down a little once you and the boat leave the lake. Dropping the body in the lake from the boat will not change the water level, since the amount of mass in/on the lake doesn't change.

The level remains the same since your boat will rise out of the water slightly because you just dropped weight out of it. If you fly over the lake with a helicopter and drop your victim the lake level will rise. An unmeasurably small amount though. (The lake level will have risen overall once you take your boat out of the water once you're done).

It was Archimides who said "eureka," not Copernicus.

What happens is the water level of the lake rises very slightly. The police, who have state-of-the-art equipment, detect the abnormal rise in water level against the background of tidal forces, realize something is up, go out onto the lake and catch you red-handed, then shoot your açç dead as you try to row away.

The level remains the same.

copernicus (eureka!)