Can You Solve this Ice Diamond Riddle? ft. Vsauce’s Michael Stevens

Water level decreases? The diamond-ice combo will displace enough water to support both, the diamond and the ice. If we think of them as separate bodies, they are both displacing enough water to support their individual weight. That means we have a LOT of water being displaced to support the diamond. In the end, the diamond isn't staying afloat, meaning that there's lesser water being displaced than there was before. The ice, on the other hand, being made of water, after melting will give just as much water as it had displaced. On the whole, I think the water level should decrease.