A coaming is a raised vertical border, frame, or sill surrounding deck openings like hatches, skylights, or cockpits on a boat. Its primary purpose is to deflect water, preventing it from flowing below decks, while also strengthening the deck structure around openings. They are crucial for maintaining a vessel's watertight integrity.

Key Details About Coamings:
Location: Common on sailboats around the cockpit area to keep water out of the seating area, and around cabin hatches.

Function: They act as a barrier to stop water on deck, such as rain or waves, from entering the cabin or storage spaces below.

Structure: Often built of wood, fiberglass, or metal, forming a frame to which hatch covers may be attached.

Coaming Bolsters: On fishing boats and some yachts, "coaming pads" or "bolsters" are cushioned pads added to the cockpit coaming for comfort, allowing crew to lean against them securely.

Coamings have been a standard nautical term since the 17th century, likely derived from "comb".