Vienna's ornate town hall threw open its doors to sea monsters, sailors and former US President Bill Clinton last night for Europe's biggest event to raise money for HIV and AIDS awareness.

Thousands of partygoers dressed in baroque wigs, fishing nets, masks, strategically placed shells and body paint downed champagne and danced until daybreak at Vienna's 17th "Life Ball" which organisers had given an aquatic theme.

The annual ball, which first started in 1993 as a party for Vienna's gay scene, has grown into a huge international event. It raised 1.4 million euros last year and drew guests and fashion designers from around the world.

"Even if it is based on a traditional Viennese ball, it is a very lively party. It is a trip of fantasy," ball organiser Gery Keszler said and added that he expected to raise over 1 million euros despite the economic downturn.

Dancers dressed as monsters, jellyfish and sea urchins splashed and writhed in a pool filled with 2.5 million litres of water in the grounds of Vienna's town hall, while a singer dressed as the ocean god Neptune boomed opera to some 40,000 spectators.

British singer Katy Perry performed after emerging from a giant seashell, while U.S. actresses Pamela Anderson and Eva Longoria took part in a parade that featured fountains, huge ship models and classical music Vienna is famed for.

Bill Clinton who opted for a traditional black suit instead of fancy dress said the 4,000 ball guests, who paid 150 euros a ticket, should enjoy themselves but remember the aim of the evening.

"Your money, the contributions you make will actually keep people alive," he said in the ball's opening speech.

"When I started this work there simply wasn't any money going around," he said, referring to his charitable foundation.

Vienna's town hall is the only political building to host an event to raise money and awareness about HIV/AIDS, which affects some 33 million people worldwide according to the organisers.

But with the number of new infections rising -- especially among women -- organisers said their work was even more urgent.

"I am from a generation where I saw my friends dying," 45-year-old Keszler said.

"There is a new generation...in all the rich countries which are not concerned anymore. They don't practice safe sex, they don't even talk about safe sex. That is a disaster in the rich countries."