What do 3 short blasts of a boat horn indacate?

Three short blasts of a boat horn typically indicate that a vessel is operating astern propulsion, meaning it is moving backward. This signal is used to inform other vessels of its maneuvering status, especially in crowded or narrow waterways. It's part of the International Regulations for Preventing Collisions at Sea (COLREGs) to promote safety and communication among mariners.