Kevin McCloud meets architectural designer Dan and interior designer Nina, who want to build a sleek, unique family house. But the plot they have bought, near a beautiful estuary in West Sussex, is dominated by a swampy pond that they are unable to fill in. Instead, they plan to make it central to their design, turning the pond into a biodiverse waterscape, and then floating their house above it. It's a challenge for anyone - but to save money, Dan is doing it largely himself, despite his limited experience with new builds