Sound signals

These are less important than hitherto – because mariners now often use the radio instead.  However, you may still come across them and on larger waterways used by ships it is essential to know the basic signals contained in the COLREGS and to use them where appropriate.

Signal Meaning
One short blast I am altering course to starboard (to the right)
Two short blasts I am altering course to port (to the left)
Three short blasts My engines are going astern (note that the vessel may still be moving forwards)

Other signals vary between waterways and you should check port or navigation authority literature for any local rules.  There are also COLREGS signals for use in restricted visibility to indicate the situation of a ship, whether it is under way, stopped, not under command, under tow, at anchor or aground (Rule 35). 

You should keep a copy of the COLREGS handy for reference concerning these signals.