Paul Allen's mega-yacht "Octopus" 2008

In 2003, Microsoft's Paul Allen - worth US$20 billion according to Forbes, the third richest man in America and 7th in the world, launched the 127m (416ft) "Octopus", which at the time was the world's largest yacht.
The Octopus cost Allen over US$200 million and has Permanent crew of 60, including several former Navy Seals. It has two helicopters, seven boats, a 10 man submarine and a remote controlled vehicle for crawling on the Ocean floor. The submarine has the capacity to sleep eight for up to two weeks underwater.