Everyone living at the coast knows the daily change between the wind coming from the sea during the day and the landfall-wind during the night. The wind moves the sea to create waves. The motion of the sea is measured on a scale from zero to nine. Force nine represents a wave height of 7 or more meters. These two stamps demonstrate the height of waves.
Storms can easily tear sails apart and break masts.
Winds and waves are able to haul over ships to one side, often causing the cargo to slide. The cargo tied to the upper deck can be washed into the sea, superstructure and hatches severely damaged and anchor chains torn. It is possible to spring a leak and big ore carriers are subject to simply breaking apart. Seas running over the decks represent grave danger for the life of seamen and passengers. They could be washed over board or smashed against the superstructure.