Virgin Limited Edition, owner of Sir Richard Branson‘s Necker Island, has unveiled the latest toy available for its guests — an “underwater plane.”

The Necker Nymph is part submarine, part airplane, allowing guests of Necker Island or the Necker Belle yacht to explore the bottom of the ocean in comfort.

Two guests, accompanied by a Necker Nymph pilot, can dive to the bottom of the sea and stay there for up to two hours, with a clear view from the open cockpits.

The craft can bank or perform 360 degree turns like a real aircraft, says the company.

Virgin claims that guests will be able to uncover ancient shipwrecks, fly side-by-side with dolphins, or frolic with whales without causing any environmental impact — the craft cannot land on reefs and has low noise and light emissions to avoid disturbing ocean ecosystems.

Unlike a conventional submarine, which uses ballast to descend, the Nymph uses downward lift (the opposite of what flies an aircraft) to descend.

The craft is designed and built by submersible firm Deep Flight, which has previously created similar vehicles for James Cameron and late adventurer and friend of Branson Steve Fossett.

Fossett’s vehicle was designed to descend to 37,000 below sea level, descending at 350 feet per second.

When taking Necker Belle for 7-nights’ exclusive hire, the sub is available at a weekly rate of €17,900 ($25,000).

For some of the time, she will be made available to guests staying on Necker Island, where rates start at around €18,000 for seven nights.

Underwater exploration is becoming increasingly popular as a holiday option, particularly in upmarket resorts.

A 7-storey underwater hotel in Istanbul (pictured below) is reportedly planning to open in 2010, as is Poseidon Resort, a 74-room underwater resort in Fiji that will also offer submarine tours.

Dubai’s Hydropolis project is now scheduled to open sometime this year after a series of delays and setbacks since 2006.