BOATsmart! USA Knowledge Base

One short blast: I’m altering my course to starboard (to the right).
Two short blasts: I’m altering my course to port (to the left).
Three short blasts: I’m operating my boat in reverse.
Five rapid blasts: I’m unsure of the other boater’s intentions.
One long blast: I’m leaving the dock and am a motorized boat of 12m or longer. 

Exception: If You’re Operating a Boat on the Great Lakes

• One short blast: I want to pass you on my boat’s port (left) side.
• Two short blasts: I want to pass you on my boat’s starboard (right) side.

During Periods of Reduced Visibility

• Sailboats should sound one long blast followed by two short blasts.
• Motorized boats should sound one long blast every two minutes.
• Boats at anchor should blast a sound signal rapidly for about five seconds every minute.