The fabulous blue of the deeper ice will haunt me. Photos capture little of it. That ice is not in fact blue, but rather crystal clear. It is very ancient compressed ice from deep layers, and the sunlight from above lights it up, and I assume refracts to generate this stunning color. I'll hazard a wild guess that it is similar to why the sky appears blue, rather than the blackness of deep space, as the light refracts through layers of atmospheric gasses. A giant chunk calved off while we watched, probably several stories high and of unknown mass. The resulting wave rocked us gently, perhaps a half mile away? I couldn't tell the distance. The water temperature around the boat was 42 F. The icebergs and currents were constantly moving. It was surreal and challenging and we had a long way to go back to the anchorage, so after a half an hour we withdrew.