Ship horns, also called whistles in maritime rules, are safety signals used by large vessels to announce movement, warn other boats and communicate in poor visibility. Short clips of a single powerful blast have become popular online as a standalone sound effect because the recording is simple to reuse. Creators lift the blast for harbour footage, cruise and ferry videos, boat memes and simulator games where a realistic departure cue is needed. Its five second length makes it long enough to feel authentic without overwhelming the scene it supports.