Sounding off on boat fog-horns

Having endeavoured to get an answer, I am somewhat bemused by the apparent necessity for the Central Pier party boats to sound their fog horns three or four times whilst departing or arriving from their berth.  

During daylight hours this is not a real problem – more a minor irritant to local residents. My issue is mostly with the sustained blasts of this ear- (and sleep-) shattering noise at night – on one occasion, at well after midnight.

With the boats lit up like Christmas trees and usually blaring music from every window, it is unlikely the horn is to inform nearby shipping of intricate manoeuvres.

I suspect that most on board know the boat is moving, so it cannot be to alert passengers.

Why then? Perhaps the operators use some fancy navigation device based on reflected soundwaves from nearby buildings (should they be piloting these boats in this case?)

Or is it simply considered all part of the game? Whatever the case, I am sure I speak for many when I ask for due consideration for local residents. Cease and desist after dark!  It’s not big, it’s not clever, it’s simply a moronic disruption of local sleeping patterns.

Perhaps I might appropriately respond by locating the owner’s house and honking my car-horn outside their bedroom window at 1am?  Although this would probably be considered breaching the peace!

Deafened of Docklands (email supplied)