This photo was taken by John Murray on a trip to the Tasman Glacier and it shows the glacier lake. There are icebergs in the foreground, the glacier in the mid-ground and Mount Cook can be seen in the background. They got off the boat at one point and walked on an iceberg. The water is approximately 80 meters deep. You can only see about 1/10th of the icebergs because fresh water icebergs sink lower in the water. These icebergs can break of the glacier way under water and come shooting up to the surface without warning. They can also roll over as they melt so you have to be very careful to watch out for any movement. Chunks can also break off and crash down making a big splash.
Picture Copyright - John Murray