German manufacturers Deutsche Composite GmbH patented the composite construction material called RexWall, a lightweight construction concept that they’ve used in floating structures for more than a decade. Using RexWall sandwich panels, their Propeta series of houseboats are motored and fully licensed for cruising, and can weather waves, tidal changes, and frost. Interior fittings can be customized. The larger model called the Propeta P12, which is close to 40 feet long, can comfortably fit up to 10 beds.