During the Three Mills Rally in 2000, a group of small craft including Dave Briant's 17ft cruiser Ursa Minor tried to get round the "navigable" semi-tidal loop of the Bow Back Rivers, with mixed success. Ursa Minor couldn't get through the combination of silt and Floating Pennywort, but the canoe and coracles did manage, albeit not without difficulty.
There seems to have been a change of person in the kayak since the last photo. Here it's Steve Burt helping Dave Briant clear Ursa Minor's blade.