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

I would say the water levels will drop. A normal ice cube will exactly displace the amount of water that it will eventually melt into (ice and water are after all the same substance but in different states). Because this ice cube has a diamond in the middle of it, it will weigh more than an ice cube of the same volume without one. When this diamond-icecube is therefore put in the water, it will displace more water relative to a normal ice cube. Because the extra weight is due to a diamond (denser than water), the water level will drop when the ice melts. In other words; the volume of water displaced by the diamond-icecube is bigger than the volume of water that the icecube could melt into plus the volume of the diamond.