She’s never had any trouble coming out of her shell.

So Katy Perry was enjoying the best seat in the house as she made a dramatic entrance at a weekend charity gala in Vienna.

The singer seemed inspired by an intriguing mix of the Little Mermaid and the Birth of Venus as she was lowered on to the stage in a giant oyster shell.

Then she shed her flowing fishtail gown to show off a sparkling one-piece costume that left very little to the imagination.

Mermaid chic: Katy Perry is lowered to the stage in an oyster shell, during her performance at Vienna’s Life Ball on Saturday night

The singer, best known for her hit I Kissed A Girl, probably won’t start any trends with her mermaid look – which included a starfish ornament in her hair and bright pink pumps.

But at least it was all for a good cause – Saturday’s marine-themed 2009 Life Ball was dedicated to raising money for those with HIV and AIDs.

The Birth of Venus: Katy recreates Boticelli’s famous painting

Attended by the likes of former president Bill Clinton, pint-sized Desperate Housewife Eva Longoria Parker, and blond bombshell Pamela Anderson, the ball drew thousands of revellers in quirky, daring, and often kinky costumes.

And it’s not the first time Katy has flirted with this philanthropic cause.

Pearl of wisdom? Katy sparkles onstage in an iridescent one-piece

Flamboyant: Katy is lowered from the rafters onto the spectacular set

Alongside Dita Von Teese, Estelle, and a host of other stars, she recently designed a T-shirt for high street fashion chain H&M – the proceeds from which will also help the fight against AIDS.

After the ball, Katy was spotted cosying up with her boyfriend Travis McCoy

The pair recently reconciled following their public split last December, with Travis announcing: ‘The break-up sucked. We`re back together now.

‘I keep thinking about if I had to go through it again and how terrible it would be. We were moving way too fast. I was being juvenile about the entire thing.

Demure: a less flamboyantly attired Katy at a press conference for the Life Ball, alongside patron Eva Longoria

‘Now it’s easy breezy. I’m happy and really in love.’

Katy is currently in the midst of her world tour, which is taking her all over the U.S., Europe and Japan.

Her UK dates include shows in London, Brighton, Birmingham, Newcastle and Glasgow next month.

I kissed a boy and I liked it: Katy Perry smooches Travis McCoy after her performance at the Life Ball