The other day I got to thinking about horns on narrowboats and if there was a code of use, after a quick google I found out that there is but I wonder how many boaters actually know about it or use it!
Thanks to where I found this out.

One short blast means: ‘I am turning to starboard (right)
Two short blasts means: ‘I am turning to port (left)
Three short blasts means: ‘I am stopping or going into reverse’
Four short and then one short means: ‘I am turning right round to starboard (right)
Four short and then two short means: ‘I am turning right round to port (left)
One long blast and two short blasts means: ‘I cannot manoeuvre’
One long continuous blast of ten seconds means ‘I am here’ and is very useful when approaching blind corners and in dense fog.