Sydney, SEPTEMBER 16: Australia's Ian "The Thorpedo" Thorpe scored a direct hit as an explosive first day of Olympic swimming on Saturday saw five world records tumble in four finals.Thorpe delivered two of them, in the 400m freestyle and the men's 4x100m freestyle relay. Michael Klim led off the relay in a world record 48.18 and Chris Fydler and Ashley Callus swam the middle legs as Australia dealt the United States their first ever defeat in the event in Olympic competition."It's an incredible feeling," Thorpe said. "It's an honour to get this gold for the country."Ukrainian Yana Klochkova warmed up the crowd in the 17,500-seat Sydney International Aquatic Centre with a world record 4:33.59 minutes in the women's 400m individual medley.Thorpe then sent the packed house into a frenzy with a world record 3:40.59.Thorpe, 17, improved on his own previous record of 3:4.33 set in this same pool at the Australian trials on may 13."This is the proudest moment of my life," Thorpe said. "I had to swim hard, but I knew I was in great form and the record proves it."Thorpe who at 15 became the youngest world champion in the history of swimming said his first Olympic gold medal was unique.Victory was especially sweet, Thorpe said, because his training since 1998 hasn't been free of disruptions."It was my most difficult preparation," Thorpe said. "I smashed my ankle in Perth, then there was the drugs controversy, and then I had to put up with the swimsuit disaster."The self-possessed teenager has not only battled back from the broken ankle suffered in May of 1999, he has adroitly dealt with insinuations of doping.As his first Olympics approached he was embroiled in controversy over his swimsuit, because he is sponsored by Adidas and Nike supplies the Australian team."I can't say what I feel like right now," Thorpe said. "It's so amazing to walk out in front of the crowd and win in front of them."Klim led off the history-making relay with a world record 100m free of 48.18 sec, bettering Russian Alexander Popov's 48.21 of 1994.The United States relay swimmers didn't go home empty-handed of gold, however.The United States women's 4x100m freestyle relay team proved there's no age limit to Olympic gold and record-breaking performances when they blew away the younger opposition to take their country's first swimming title of these Games.Jenny Thompson achieved a record-equalling six Olympic gold medals, as she anchored the US team to a time of 3:36.61 minutes that eclipsed China's 1994 world record of 3:37.91 minutes. The combined team of Thompson, Amy Van Dyken, Dara Torres and Courtney Shealey, had at 27 years the highest average age of all the relay teams, with 33-year-old Torres, the first American to swim in four Olympic Games, the oldest swimmer on the team. "It's a tremendous honour to be on the relay team with Jenny and Amy and young kid Courtney here. We're showing people you can't put age limitations on your dreams and you don't have to be a teenager to win a gold medal," said Torres.Torres retired after the Barcelona Games, but decided to make a comeback seven years later in 1999. Thompson, who equalled Kristin Otto's six Olympic gold medals, said that she was delighted with the achievement, but still dreamed of an individual gold as all her titles were in relay events. "I want to thank these three here and all the numerous others over the years," said 27-year-old Thompson, referring to her past Olympic relay partners. "I don't think I feel any sense of history yet. This is only just the beginning and I'm only thinking about this meet and not what I did in the past or the medals tally."