The places where the glaciers reach the sea contribute to the formation of icebergs. Newfoundland and Labrador attracts many tourists because of its icebergs and fjords. Concerns included icebergs and collisions with whales. These shelves then melt or calve off to give icebergs that eventually melt. Polar bears occasionally visit the island, travelling on icebergs from Greenland. This voyage was recreated by Tim Severin, suggesting that whales, icebergs and Rockall were encountered. The finale was diving underneath Antarctic icebergs alongside predatory leopard seal. Small bits of disintegrating icebergs are called "growlers" or "bergy bits". The orca separates the icebergs, trapping Nolan. The NIC is the only organization that names and tracks all Antarctic Icebergs. Flocks are characteristically seen sitting on icebergs. Both are generally spawned from disintegrating icebergs. Systems for detecting icebergs and U-boats were developed. On 28 June "Pinguin" headed south surrounded by icebergs. Icebergs, especially in May to October, make the area even more dangerous.