According to Kent Online, A pizza "buoy" in a full wetsuit sets out in a canoe to deliver to houses along the river. To make sure that the pizza doesn't get waterlogged if the canoe happens to capsize, it comes in a delivery bag that floats.
Considering the company has also tested drone delivery in the UK as well as a few other countries, canoe delivery seems to cater to too small an audience to gain any real traction.
Additionally, the delivery test is only running for two weeks.
Photo via Domino's UK.