Roger Federer, Rafael Nadal Play Tennis on Water in Doha

Doha Bay, Qatar:  It was an unusual tennis experience as the world's top two male tennis players, Roger Federer and Rafael Nadal, played on a special water court ahead of the season opener in Qatar.

The water court had been constructed in the waters of Doha Bay.

The two are the top seeds at the Qatar Open that begins today, and will again be the players to beat during the 2011 ATP World Tour season, which comprises a total of 63 tournaments in 32 countries.

Spaniard Nadal will begin the event as top seed.

"The best of the history is here, Roger and a lot of very good players, former champions, (Nikolay) Davydenko, (Jo-Wilfried) Tsonga, (Philipp) Kohlschreiber, (Ernests) Gulbis, (Viktor) Troicki - lot of very good players are here so it's going to be a really interesting hunt for sure, competitive tournament," said Nadal.

Two-time champion Federer is next in the list of eight seeded players. After beating Nadal in the 2010 season-ending World Tour Finals, Federer is excited to begin his 2011 campaign.

"Now I'm really prepared for it. The break wasn't very long, which I think in this case is quite an advantage for me because I played so well at the end, so I actually haven't lost much of my game and I feel like I'm actually playing pretty well already," Federer said.

Nadal and Federer have won 21 of the past 23 Grand Slam singles titles.

Later this month in Melbourne, Nadal will attempt to become the first player since Rod Laver in 1969 to hold all four Grand Slam trophies at the one time, while Federer will look to add to his record haul of 16 major titles.

In 2010 Nadal won Roland Garros, Wimbledon and the US Open, where he completed a career Grand Slam, en route to finishing year-end number one for the second time.

Federer, whose strong finish to 2010 included a fifth title at the ATP World Tour Finals, will be the defending champion in Melbourne.

Nadal and Federer will, though, have plenty of competition throughout the season as world number three Novak Djokovic, world number four Andy Murray and world number five Robin Soderling continue to turn up the heat.

And plenty of interest surrounds the return from injury of 2009 US Open champion Juan Martin del Potro, and the performances of players like Tomas Berdych, David Ferrer, Andy Roddick, Fernando Verdasco, Mikhail Youzhny, Jurgen Melzer, Gael Monfils and Jo-Wilfried Tsonga.