Let’s talk about ice and water and how they interact with light. A great question by upallnightathogwarts asked: “Why is snow white, but ice and water are see-through?" Snow looks white, even though it’s just ice, and clouds look white, even though they’re just water.
For example, check out the picture above where the guy is looking through the ice. If he were looking through that same amount of snow, you wouldn’t see his face—you would just see the snow. Let’s think about what “see-through” means. It means the light comes through in a straight line without changing. For example, his hat is dark but his face is light. So to “see through” the ice, the light rays coming from his hat (dark ones) and his face (light ones) have to transmit through the ice to our eye (or camera) without changing too much.
(See-through ice picture by wewe94 on deviantart. Check it out.)