Howard and Sarah embark on their most ambitious building project yet - a sleek, angled, metallic floating home on a tidal estuary near Worthing. Designed to look like a boat, and nestled within an idiosyncratic houseboat community, the structure will sit on an experimental prefabricated polystyrene slab to deal with high tides alternating with hours sitting in the mud. It's a huge experiment, with £385,000 to spend over an 18-month schedule, especially as they'll be doing much of the work themselves and finalising the engineering as they go. Things get off to an agonisingly slow start when it takes months to painstakingly remove a condemned D-Day landing craft from the plot before they can even get started and the constant tidal shifts that disrupt any construction creates a real recipe for disaster