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

1:53 When you said "You know the..." I thought you were going to say "you know the answer" and I was going to be like yes, yes I do. XD

For the second riddle: assuming the ice cube has not fully melted, if the ice detaches from the diamond then the water level will go down as the ice rises out of it. But if the ice remains stuck to the diamond then it will get dragged down with it and the water level will go up. I'm leaning on the latter because I think the ice will trap the diamond inside as it melts around it, but the former seems a definite possibility. In either case, the difference will be so minor it could be difficult to measure.