Ten years ago, François-Alexandre Bertrand had an idea for a novel watercraft that cruised to a site and then lowered its passengers below the water to have a look around. We got to see the first renders in 2011, a working prototype followed in 2013 and as production plans were announced, we got to experience an underwater adventure off the coast of St Tropez in 2016. Now the first Platypus Blue Ocean has been sold, and the order books officially opened.

Originally conceived as a two person craft, the thinking was to cater for underwater explorers who had no diving experience by having them put on a facemask and then submerge the center section of the Platypus to a depth of up to 1.5 meters (5 ft). Air would be supplied to the passenger and pilot and a long air hose would cater for exploration beyond the craft itself, if desired. And that's what 2013's prototype delivered, more or less.

The original proposal was to fit out the Platypus with electric offboards so that it could stealthily navigate the lagoons and coastal waters it was deigned to explore. But the prototype relied on two Mercury engines due to the range limitations of electrics.

"We had two 4 kW Torqeedo motors and 12 kWh of batteries and we reached an average speed of 10 knots, which was really good, but the range on the lake was 30 miles," Bertrand told us in 2016. "In the sea we could only go up to one hour and thirty minutes, which was too limited."

Needing to prove the craft, combustion engines were chosen. Unfortunately, the location of the intake tube for the hookah system on the prototype – which allowed underwater explorers to breath – was a little too close to the hydraulic system, which resulted in a lovely fuel taste to the air.

But everything else worked as advertised. "On paper, the Platypus looks impressive, mold-breaking, innovative," we noted. "In the flesh, even more so. But going out on what was effectively my first dive without needing any special equipment, no special training and little more than a few swimming certificates to my name was a real eye opener. No tanks on my back, wearing just a t-shirt and shorts and riding pillion beneath the waves on something akin to an underwater motorbike."

Bertrand revealed a new design for the Platypus during our visit, which would cater for more passengers, be fashioned from aluminum with a sleeker look, and rock a central pod that served as an extra hull – instead of being raised above the waves – when the craft was in boat mode.

By the end of 2017, this final version jumped from the drawing board to reality courtesy of CDO Innov and testing was conducted at Noirmoutiers in the Bay of Biscay, followed by a new paint job and subsequent showing at a diving expo in Paris. A purchase deal was struck with Sebastien Charbonnier of New Caledonia's Seascape, who insisted that the Platypus did not leave France until it was perfect.

Bertrand has just returned from Noumea, after the successful delivery of the Platypus Blue Ocean to Seascape – and the completion of the first sale. This craft is homologated to carry five people, including the pilot, and is able to travel almost 20 knots in boat mode.

This 7-m-long, 2.5-m-wide (22.9 x 8.2 ft) Platypus has a catalog price of €167,500 (about US$190,350), and features a 360-degree digital periscope to keep an eye on what's happening above the waves while everyone is below, two hookah systems that support up to five occupants and LED lights for after dark underwater adventures.

It comes with two 50 hp gas outboards for a top surface speed of 18 knots, but can be optioned up to 80 hp for 24 knots or made fully electric with two 10 kW motors and a 20 kWh Li-ion battery pack, which top out at 10 knots. Underwater navigation speed is limited to 3 knots. Other optional extras include underwater cameras, a waterproof case with GPS and an underwater comms system.

The batteries that power the hydraulic lifting arm and hookah system are reported good for up to 60 raising and lowering operations and 4 hours of underwater air supply, respectively.

A number of variations have now been added to the sales catalog, ranging from a basic Pro configuration at €125,000 to an all-electric yacht model at €575,000. Proposed applications include shallow water research and exploration, marine tourism and recreational pursuits.

You can see the first production Platypus in action in the video below.

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