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

The water level depends on the ratios of the ice and the diamond, specifically, you can tell whether it goes up or stays the same by looking at the ice cube, if the ice cube is above the water, when it melts, it adds to the water, but if the diamond is big enough, the ice cube doesn't float at all. In this case, all the water is below the water line to begin with, so it doesn't rise. You can argue that it might even go down, because of the difference in volume based on temperature, but I didn't think about it.

By the way, I always thought it was fascinating, the single moment when the vertical speed of the ball is zero. I first noticed it when I was looking at a graph of the ball's speed as a function of time. That single point, where the speed is zero, just amazed me, and I am thinking about how small that moment is eversince.