Six-time Olympic champion Michael Phelps has hailed the achievements of Ian Thorpe following his retirement.
Van den Hoogenband, Thorpe and Phelps shared the medals in the 200m freestyle in Athens
"Ian was an inspiration and a terrific champion," said American Phelps. "He elevated the worldwide interest in swimming and was a great ambassador."
Phelps, who won eight medals, six of them gold, at the 2004 Athens Olympics, was one of Thorpe's major rivals.
The two were due to clash next March at the World Championships in Melbourne until Thorpe decided to end his career.
Pieter van den Hoogenband, who split Thorpe and Phelps in a memorable 200m freestyle final at the Athen Olympics, said he would miss competing with the Australian.
"Thorpe forced me to push myself beyond my limits," said the Dutch 28-year-old.
"I would have liked to swim against him one more time on his home ground at next year's world championships in Melbourne.
"It will feel strange not to swim against him again. I'll feel like a fish out of water not having this big black fish beside me."
Praise has poured in for Thorpe following his shock announcement.
"He rates as the greatest freestyle swimmer in the world," said fellow Australian swimming great Dawn Fraser.
Australian prime minister John Howard added: "His retirement is an enormous loss to Australian swimming.
"Millions of Australians will remember his wonderful individual performances."
Fraser said she had hoped Thorpe would match her achievement of winning gold at three consecutive Olympics.
In 50 years from now, Australians will still marvel at the feats of Ian Thorpe
Australian Olympic Committee president John Coates
"I guess in a way I'm sad but that's selfish of me," said Fraser, who won the 100m freestyle at the 1956, 1960 and 1964 Olympics.
"Ian, I thank you for what you've done for Australian swimming - now go off and enjoy your life."
Shane Gould, who won three gold medals at the 1972 Munich Olympics before retiring at 16, said she understood his decision.
"He could probably swim faster and I could probably have swum faster and won more medals but look, swimming's just swimming - there's a whole life out there," she said.
President of the Australian Olympic Committee John Coates said Thorpe's achievements would stand the test of time.
"In 50 years from now, Australians will still marvel at the feats of Ian Thorpe," he said.