This is caused by bubble free melt water refreezing in the cracks or crevices of the glacier as it crept to the coast. This does not mean that the ice underneath the water is six or seven times deeper. It is six or seven times larger in mass. I cebergs are very variable in size. These are usually pieces that break off from larger icebergs.
Growlers can range from a small car to a large house in size.
Bergy bits are even smaller. These icebergs can still be very dangerous to shipping because they are often low on the water, hidden by choppy seas and they are sometimes invisible to radar. It's a spectacular site. The tallest arctic iceberg was spotted in 1967 which towered some 550 feet above the ocean surface. This is about half the size of the Empire State Building.