If you have individual British Canoeing or national association On the Water membership you alone are covered. If you have couples or family membership then all people covered in the membership have a waterways licence.
The principle of the licence is that the craft a member is paddling is licensed on the water, so long as the member is actually in or on the craft.
Any member may take non-members passengers in a craft. However, the craft is unlicensed if the member is not on board. Passengers do not have third party insurance.