Answer 1

Icebergs are huge masses of ice floating in the sea [density of ice being 0.917 g Cm^-3] with about 9/10 portion of ice below seawater and only 1/10 portion of it above. Since such a large portion of the iceberg is submerged underwater it becomes difficult for the sailor to estimate the size of the iceberg increasing the danger of the ship colliding in them.