In the world of nautical design, secrets don't stay very hidden for long. But bobbing up and down at the end of the harbour wall in Port de Saint-Jean-Cap-Ferrat, just opposite the Club Nautique, is a boat that has never been seen in public before. This is the Arrow 460 Granturismo, the first fruit of a partnership between Mercedes-Benz Style and Silver Arrows Marine. A sleek, silver cabin cruiser, it is the fruition of many years' development.

The boat broke cover as a concept back in 2013, with the intention of translating MB's design language and technological know-how into the notoriously conservative marine sector. Under design director Gorden Wagener, Mercedes is pushing hard into the 'modern luxury' sector, hoping to become a dominant force in the world of sybaritic futurism. The boat is joined by new ventures into lighting, interior design and even aeronautical interiors, all of which share a common aesthetic of seamless, fluid spaces, new materials and the careful integration of digital systems.

The Granturismo is intended to be ocean-going super coupé, designed to ride on the water like an S-Class slices smoothly across the tarmac. The unveil took place during the launch of the new S-Class Cabriolet, Mercedes' biggest open-topped car to date and a machine that Wagener describes unashamedly as a 'land yacht'. Of course there are visual similarities – two great silvery superstructures with unfurling, electronically operated canopies – and of course there will be client crossover. The Granturismo plays slightly uncomfortable tricks with scale, especially with that car-like side profile. On the water, at speed, it looks like nothing else and the proportions belie its true size. On the deck itself, the minimal detailing is at odds with the traditional superyacht-style maximal approach.

Wagener claims that the final design is 95 per cent identical to the original concept models, although Mercedes' rigorous insistence on certain details challenged the fabricators at Silver Arrows Marine. The boldest elements on the exterior are the glass, in the shape of the huge one-piece side windows that retract into the bodywork in the manner of a car, and the hydraulically raised front glass that opens up the interior, creating the effect of 'loft living on the water'. The first boat doesn't have a finished interior just yet, although the glass is working seamlessly. Ultimately, this will be a concoction of fluid spaces, with a retractable table and bed that lets the entire volume stay as open as possible. Specially developed bent wood veneer and moisture-leeching breathable fabrics form the bulkheads and seating, making the entire boat a truly modern statement.

As Mercedes' Uwe Hörnig, the man responsible for overseeing the S-Class Cabriolet's development, pointed out, the company's three-pointed star originally stood for transport superiority in three realms, air, land and water. Along with the recently revamped interior of the Eurocopter EC145, the Granturismo fulfils this vision, albeit on a fraction of a scale of their passenger car business. There are of course other manufacturers looking for a slice of the nautical action, most notably Aston Martin with the newly launched AM37 powerboat designed with Quintessence Yachts. But as Mercedes is quick to note, only their boat has been created from scratch. The Granturismo takes Mercedes-Benz’s design language into a new realm, creating one of the most exclusive applications of the three-pointed star in the process.