Vehicles such as the EGO semi-submarine boat and Adventure-Doo are designed to bring the underwater action within reach of those without the time or inclination to put in the training required to get behind the controls of personal submarines like the offerings from U-boat Worx. But the Platypus underwater exploration vehicle from François-Alexandre Bertrand ditches the waterproof hull while giving users a taste of life beneath the waves. We first looked at the Platypus in concept form in 2011 and a prototype has now hit the water as it navigates the often-treacherous waters to commercial availability.

"The submersible has existed for a long time, but with a big bubble," Bertrand tells Gizmag. "We're the first to offer an up position in order to navigate like a boat, and a submerged position where you are under the water to navigate – totally free, wearing just a swimsuit."

The Platypus is basically a catamaran with a central platform that the passengers straddle. Two pivoting arms connect the two hulls to the platform, which can be hydraulically lowered under the water. In this way, the users can cruise around above and, with the aid of an in-built air compressor supplying oxygen, below the water's surface.

Measuring 5.7 m (18.7 ft) wide, 2.46 m (8 ft) wide and weighing 720 kg, the prototype is propelled through the water by two Torqeedo electric motors powered by a 10 kW lithium-ion battery pack. With the passengers above the water, it boasts a range of up to 30 nautical miles (34.5 miles/55.5 km) when traveling at an average speed of 5 knots (5 mph/9 km/h), but can reach speeds of up to 10 knots. This drops to less than half when the passengers are below the water, with the battery lasting for around four hours with a standard mix of surface and diving modes.

However, the company also plans to produce a model powered by two 9.9 hp Mercury engines that will give the craft a surface mode speed of up to 14 knots (16 mph/26 km/h) and greater range. In surface navigation mode, the central nacelle sits about 50 cm (20 in) above the surface of the water, which Bertrand told us "gives the impression of flying over the water." In dive mode, the passengers are about 2 m (6.5 ft) below the surface.

After the first underwater tests at the Bassins à Flot in Merignac in Bordeaux earlier this year, where Platypus Project Manager Rachida Ettarfaoui came face to face with a dead rat, prototype testing moved to the much more inviting coastal waters of St Tropez in September. "It was the first time we could use the Platypus in the kind of environment it was designed for," says Bertrand.

An early prototype had the air intake placed inside the floats, however, during testing the team found that the air fed to the submerged passengers had the less-than-desirable smell of hydraulic oil. For this reason, the final prototype version pumps air to the passengers from outside the craft using an electric air compressor.

Bertrand told us the production version will also offer a 20 m (65 ft) extension air tube as an optional extra that can be attached to the onboard air supply to give passengers the freedom to get off their seat and swim away from the craft. There are also plans to include space under the seats to stow air tanks for passengers who crave greater freedom. For the even more adventurous or for research purposes, there are plans to offer a shark cage as an optional extra.

"We are still designing the final version, that is going to be quite different from the prototype you see today," says Bertrand. "Firstly, we are going to have a rear platform, as you can see it's only a catamaran today, as we noticed it was an issue that you don't have the space in order to work on the Platypus. With today's shark cages, you cannot move out and say hello to the sharks, it's not very secure. So with the final version, we are going to be able to integrate a deploying cage into the mechanism, as an option. We propose a mobile shark cage, between the four hydraulic arms holding the nacelle, we are going to have smaller arms for the cage." Bertrand says the plans for the shark cage should be completed early next year.

The current prototype is pre-homologated as a category C boat for use in areas close to shore, with Bertrand saying the final version will be CE homologated. France-based naval architect firm Van Peteghem Lauriot-Prévost (VPLP) is helping to finalize the Platypus design and French entrepreneur and businessman Xavier Niel is on board as the project's main investor. However, the Platypus team is about to embark on another round of fundraising to get the vehicle over the line and into production.

Bertrand hopes to have the first units due for a release around March/April of 2014 and the company plans to take pre-orders before the end of this year with potential buyers required to put down a deposit of €5,000 (US$6,750) for a "Classic" Platypus. The company is aiming for minimum starting prices of €42,000 (US$56,700) for the ICE-engine powered model and €50,000 (US$67,500) for the electric version.

The Platypus prototype can be seen being put through its paces in the following video.

Source: Platypus