Ahhhh... it was the PLA's idea, that is why I couldn't find anything in the COLREGS!
Thanks for the reply. We have toyed with the idea of a flashing yellow, but for use as a warning light similar those on construction vehicles, for use when we are setting seine nets from the shore in the upper tideway. I have noticed them being used by the PLA Driftwood and salvage boats in this kind of way, and it may prevent us catching a few irate rowers. Because they all
look over their shoulder every third stroke, just as they are supposed too...
Hope that you had a good day out.