Actress Melissa McCarthy was left with a bruised ego while practising a stunt for her new movie after flying off a jet ski and losing an expensive wig before filming had even begun.

The Bridesmaids star was determined to perform a water stunt for one scene in Tammy herself, despite having little prior experience on a jet ski, so she decided to go for a test run with her stunt co-ordinator - complete with her character's pricey hairpiece to make sure it would stay in place during the shoot.

However, her safety check didn't go quite as planned and she soon ended up underwater, ruining the wig.

She says, "I wanted to do it (the stunt) myself. I had been on a jet ski for 14 minutes in my life at this point... So we were out there and this is the safety check and I'm out there with the stunt guy and he's walking and talking me through everything...

"I have this wig that cost an unbelievable amount of money... so I got the wig on, there's like 35 pins in my hair, it's not going anywhere and I'm out there and... I got a little cocky.

"I'm now going about 40 (miles an hour) and in my head I'm like, 'I don't know why I don't do this professionally...' So I'm like, 'S curve time.' My very first one I'm thinking I'm going to like, dazzle them and literally on the first one it (jet ski) brakes, I flip over it and I'm under water before I know I'm off the jet ski. It's an incredibly violent fall and I'm like, so deep I don't know I'm under (the water). I don't know which way is the sky. I'm literally like, 'Just let it go and you'll float...' and I came up to the top... and I'm like, 'I lost the wig.' We had to rush and get another wig made, I'm like, 'I'm sorry guys'."