I've noticed that if you take a full glass of water and look from above, through the water, you can't see through the glass sides - instead, you see a reflection. I tried with a laser pointer and the case was the same, the beam was just reflected from the water-glass interface. Even when looking from a variety of angles the case is the same. With no water in the glass, you can see through it fine.
Why is this?
A little research (Wikipedia) suggests that you can get Frustrated TIR from tightly grasping the glass, so photons can tunnel through from inside the glass of water, get reflected by skin and then tunnel back to get to your eye (again, I think this is right).
However, I wonder what physical mechanism prevents light from escaping a glass of water?