Here is a complete, single-file HTML solution using Three.js. It creates a 3D interactive scene of your seastead design with the specific dimensions, materials, and configuration you described.
You can save this code as an `.html` file (e.g., `seastead.html`) and open it in any modern web browser.
```html
Seastead Design Visualization
Seastead Design: 40x16 Living Area, 45° Legs, Submersible Mixers
```