DESIGN The Couach 1500 has curvy lines and a graceful shape that give her the look of a sports car.

Fluid may be the best single- word description of the Couach 1500. The curves that define her overall shape play with one another so well that we scarcely notice their individual contributions or where one merges with another.

Tracing the sheer line from the bow reveals a subtle incline, but the line remains straight for a bit more than half of the boat’s length. A lounge fills the foredeck, and the superstructure surrounding the area gradually rises to form the base of the deckhouse. This increase in height makes the sheer line appear slightly reverse. The effect is fairly straightforward and common, but then the sheer line sweeps upward before beginning its descent to the swim platform. How can any motif as graceful as this be so muscular? The profile reminds me of a flexed bicep. On the practical side, that structure formed by the upward sheer line creates a bulwark to protect the wide side decks.

One of the difficulties designers face is breaking a large mass into attractive segments. Clement Carbonne, the French builder’s in-house designer, accomplished this by drawing one of the coolest deadlights in the business. Its top edge quotes the sheer line; its bottom edge follows suit. At each end, edges raked at opposite angles will intersect virtually below the waterline. That convergence is important because angles used to delineate a shape are happiest together when a line extended from each intersects its mate somewhere short of infinity. The thick rubrail also helps disguise the mass of the topsides.

While we’re on the subject of rake, notice how the angle of the C-pillar at the after end of the deckhouse, the ski-jump slope of the transom, the rail stanchions and the stem echo one another. Although this continuity may not shout its importance to the boat’s overall look while underway, we likely would see the ill effects if it were disturbed.

From a distance, the deckhouse resembles a seamless canopy, but on closer inspection we see a raked windshield anchored by the superstructure’s nicely tapered A-pillars. This windshield looks fabulous from the outside; equally important, it floods light to the helm and companionway inside. Large side windows that are nearly perpendicular add light and increase the saloon’s sense of open space. Eliminating significant tumblehome in the sides of the house opens up space in the saloon.

Despite the Couach 1500’s contemporary profile, her arrangements plan is traditional. The main deck is a single level from the transom to the helm. An L-shaped settee on the port side faces an entertainment center opposite, and immediately forward of that is the galley. The port-side helm has two seats. This layout encourages mingling at anchor and allows the helmsman to be part of the scene while the boat is underway.

Wide side decks, substantial bulwarks and rails allow safe passage fore and aft — from the afterdeck to the foredeck. Side decks have made the list of endangered features on many 21st-century boats, but they are an essential part of the Couach 1500. The seating plan on the afterdeck converts from a settee, accompanied by a table and freestanding chairs, to a dining area for as many as eight.

Below deck, the symmetrical arrangement places a pair of mirror- image staterooms amidships and a master in the bow. Two identical heads are here, too: a starboard side en-suite for the master stateroom, and a portside head for the guest quarters and for use as the day head. C’est un bateau doux!