Captain's Protest is a document filed by the captain of a vessel to report and document any discrepancies, damages, or losses that occur during a voyage or while the ship is at port. It serves as an official record of the captain's observations and protests, providing evidence and protection for the vessel's owner and crew. In the supply chain, a Captain's Protest can be used as supporting documentation in insurance claims, disputes, or legal proceedings related to cargo damage, loss, or other maritime incidents.