While out in the zodiacs for an iceberg cruise, we tried to return to the ship and discovered that the wind or tides had caused the ice bergs (bits fallen from a glacier) and ice flows (frozen sheets of sea ice) to be forced together, closing the gaps through which we had come. We probed every part of the exit from the bay and found no exit. We could see the ship, but we couldn't reach it and the fog was coming in again. So an experiment was made to see if the largest zodiac (full of people) could break the ice with its weight. The zodiac was driven at full speed onto the thinnest looking ice flow, and it broke up under the weight. The zodiacs followed in a convoy and we returned to the ship. Zodiacs are not supposed to be used as icebreakers!