The yacht has become, in recent years, the ultimate expression of wealth and power. It seems that you can't be in The Forbes 400 top of the richest people on the planet without owning a kick-a** yacht, or was it the other way around?

Originally, it was defined as a light, fast sailing vessel used by the Dutch navy to pursue pirates and other transgressors around and into the shallow waters of the Low Countries, but later it came to be used to transport important persons.

And it still is today, when private yachts have evolved from fairly simple vessels with basic accommodation to sophisticated and luxurious boats.

A new breed of yachts appeared in the last decade, as the richest and most famous people in the world wanted to stand out from the crowd of the "simply rich" individuals. These are often referred to as Megayachts.

But which is the world's biggest yacht? A few names distinguish themselves through size, luxury and price. Sigma is a 118 meter-long (387 ft) megayacht designed by Phillipe Starck and built by the elite Blohm + Voss ship-building facilities. It costs more than $200 million.

The second largest is the 138 meter Rising Sun, the biggest megayacht in the world, owned by Oracle Software founder, Larry Ellison.

And the winner is...unnamed. Yet. The biggest yacht in the world is still under construction in a port in Germany, but no pictures are yet available for the general public. When finished, it will be the grand master of superyachts.

Known only by the codename, M-147, it will have its own helicopter landing pads and an integrated submarine. It will also have various loggias, balconies, oriels and sun decks. The loggia will stretch over the whole width of the yacht, and will connect the dining room to the main salon.

The stern of the ship will be made of one continuous stretch of glass, offering an impressive 270° panorama view. In addition to the already outrageous facilities, it will also be equipped with a swimming pool on the upper deck, a cinema and a disco.

The technical specifications provided by the builder are more than impressive. The megayacht will be 147.10 meters long (482.6 ft), 21.5 meters wide (70.5 ft) and will have a 5 meters (16.4 ft) draught. It will have a maximum speed of 25 knots.

No one knows how much it will cost, and the rumors have it that the proud owner will be Russian self-made billionaire Roman Abramovich, mostly known for being the owner of the Chelsea football club.