A vessel gives one long blast near a blind fairway section. What is the sound signal communicating?
Short answer
Caution that other traffic must interpret with the developing waterway context
The governing principle is that one long means caution, not a claim to the fairway. Treating it as permission fails because sound cannot prove the route is clear. Locate the vessel, control speed and interpret the blind-section context before proceeding. Revisit General Signals: Meaning and Immediate Response.
Quick check
A vessel gives one long blast near a blind fairway section. What is the sound signal communicating?