If you are a tidal Thames paddler and use a flashing light, please ensure it has a regular frequency and cannot be mistaken for Morse Code.
Earlier in January there was a major Search and Rescue call out on the River Thames in London when an alert member of the public spotted a light flashing SOS in the river and called the coastguard. Fortunately it emerged that it was just a paddler who had chosen a light that flashed in that code. The Port of London Authority allows for a white flashing light to aid visibility as an addition to the normal white light.
See - http://www.boatingonthethames.co.uk/Paddling
The authority is firmly behind canoes and kayaks being lit on the river, but this is not quite how they would like to see it done.