When it comes to the polarising, mind-bending lines of the 135-foot superyacht Ocean Emerald, there are no middle grounds.

This arcing reach of its grey steel superstructure. As the roofline swoops down to meet the bow, it is awkward and unpleasant. Those harsh horizontal bars along the flanks could be mistaken for bars on a penitentiary cell. Nonetheless, if you see Ocean Emerald anchored anywhere from St. Bart’s to St. Tropez or Capri to Cape Cod, you can expect an infinite stream of Instagram posts.

In 2009, when the yacht was unveiled, she defied convention by breaking every rule. Which is precisely what her designer, the renowned British architect Lord Norman Foster, had in mind. The 85-year-old Foster is not conventional. He has given the world such iconic structures as 30 St. Mary Axe in London, also known as the “Gherkin,” the spaceship-like Apple campus in Cupertino, California, and the yacht-like Yacht Club de Monaco.

This eccentric superyacht was inspired by one of his most famous quotes: “As an architect, you design for the present, with an awareness of the past, for a future that is essentially unknown.”

Ocean Emerald wasn’t his first foray into superyacht design; that was the 190-foot Lürssen-built Izanami, which was launched in 1993 (and renamed Ronin by Oracle’s Larry Ellison). However, she was without a doubt his most contentious. Ocean Emerald was constructed by Rodriguez Yachts with an aluminium hull and a composite superstructure. A pair of 1,400-horsepower Caterpillar diesel engines generate a maximum speed of 18 knots and a comfortable cruising speed of 14 knots.

There are floor-to-ceiling windows, enormous decks for entertaining, and three flights of wide teak staircases at the stern to give visitors a workout as they ascend from the water level to the jacuzzi on the top deck. There are accommodations for ten passengers in five cabins, as well as nine crew members. The expansive owner’s suite is located on the main deck at the very front of the yacht, with views of the bow.

Ocean Emerald was one of three identical designs constructed between 2009 and 2010 for the YachtPlus fractional ownership programme. The concept was that a purchaser of an eighth share would be guaranteed 30 nights per year on board. These would be divided between the Mediterranean and the Caribbean, with access to Ocean Emerald, Ocean Pearl, or Ocean Sapphire, or their sibling yachts. Lord Foster was one of the company’s primary investors. The endeavour ultimately failed, and the yachts were sold. Ocean Emerald was acquired by Nigel Plaskett in 2013 and relocated to his home base in the Gulf of Thailand. He has been chartering the yacht there for 10 weeks per year at a weekly rate of approximately $113,000.

If Ocean Emerald appears familiar, you may have seen her in the movies. Before Plaskett purchased the yacht, she made her film début in the remake of the 1991 high-adrenaline cult classic “Point Break,” starring Keanu Reeves and the late Patrick Swayze. The yacht was used as the setting for a rowdy party sequence filmed off the coast of Brindisi, Italy.

“No, it wasn’t love at first sight,” Plaskett told Robb Report regarding his initial impression of the yacht. “However, I do enjoy items that are distinct and unusual. And Ocean Emerald certainly fits the bill.”

The engineer of British descent explained that the yacht’s interior space, which was approximately 30 percent larger than a typical yacht of this size, soon won him over. During the seven years that Plaskett has possessed the yacht, he has commissioned two complete interior renovations using Thai artisans. The most recent renovation, which was completed last year, saw the yacht’s interior become ultra-modern to match its dramatic exterior. Plaskett states that she has been a very successful charter yacht. “Of course, nobody else is chartering here in the Bay of Thailand. Russians in particular adore her because she is so unique.”

Ocean Emerald was rumoured to have cost more than $24 million to construct, but she is now available for $6.86 million through Camper & Nicholsons. Need two? Ocean Sapphire, the yacht’s sistership, is also for sale with Zurich-based Schmidt Yachting for $6.98 million. Just don’t expect to sail in either yacht without being observed.