Coaming is any vertical surface on a ship designed to deflect or prevent entry of water.
It usually consists of a raised section of deck plating around an opening, such as a cargo hatch.
Coamings also provide a frame onto which to fit a hatch cover.
The protective metal sheeting or plating protecting against water entry into ventilation shafts in large ships is called a coaming as it fulfills the same water-deflection purpose.
The term was borrowed by the aviation industry to refer to a low rim around the opening for an unenclosed cockpit.