Michael Phelps, the multi-gold medal winning Olympic swimmer, has signed a four-year extension to his multi-million dollar endorsement deal with Speedo.

Phelps appeared on CNBC with Darren Rovell to discuss the deal, saying: "If you think about it, I’ve been with the brand since I was 16. And it has been the only suit that I’ve ever worn in my life."

Phelps has been backed by Speedo since 2001, and will now continue to be sponsored by the company until 2013. That partnership will take in another Olympic games, in London in 2012.

Amusingly, with hindsight, Phelps' first deal with Speedo stipulated that the company would pay for his college education in case his swimming career didn't work out. The company handed him a US$1 million bonus for his performances in Athens and Beijing. Phelps donated the bonus to charity. 

Phelps' image has suffered somewhat out of the pool this year, with a recreational drugs-related suspension and an order to appear in court after a car crash in Baltimore. However, his prowess in the pool is unquestioned, with eight Olympic gold medals in Beijing following six in Athens. He has won 45 gold medals in major international competitions.

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