"Thes chunks of ice pose a serious threat to the ship as it moves through narrow waterways. A collision with on will create multiple Hull Breaches, wasting precious time." - Dread Hunger Compendium.
Icebergs are spawned to block the ship from moving forward, if the ship hits an iceberg, it will cause the ship to create 3 hull leaks.
There is a large iceberg spawned at the end of a map, and it has a lot more health than a normal iceberg. It is impossible to break it without Nitroglycerin. The Iceberg on Archipelago (Totem Mod) can take up to 3 nitro detonations before it’s destroyed, preferably deployed at the same time, as the ice on the water before it will also break, making it difficult to get close enough to it.