Selena Gomez has hit out at the ''beauty myth'' in society which she claims ''traps modern women''.

The 25-year-old singer and actress posted a video of herself messing around with friends onboard a yacht in Sydney, Australia, where she was snapped sunning herself and snacking on an avocado.

Selena captioned the clip: ''The beauty myth - an obsession with physical perfection that traps modern woman in an endless cycle of hopelessness, self consciousness, and self-hatred as she tries to fulfill society's impossible definition of flawless beauty. I chose to take care of myself because I want to, not to prove anything to anyone. Wind in her sails.''

The 'Heart Wants What It Wants' hitmaker is thought to have rekindled her on/off romance with boyfriend Justin Bieber who she has dated on and off since 2011.

To mark his 24th birthday Selena took to Instagram to post a picture of herself holding a polaroid which appears to be a photograph of Justin. She wrote: ''March 1, 1994 someone I know that happens to be super cool was born. Boom. (sic)''

Justin is not with Selena on her current trip to Australia, where is seen messing about in her video with friends, including two unidentified males.

It has been reported that Selena's pals think Justin is a ''bad influence''.

A source said: ''There's a big crew of people [in Selena's circle] who really don't like Justin and they especially don't like him with Selena. A lot of her friends really don't like him. They think he's bad news for Selena and don't approve of the relationship. They think he's a bad influence on her and she becomes really dependent on him. She's so generous and loyal and puts 100 per cent of herself into everything, including her relationships, which isn't always the healthiest.''

The 'Wolves' singer's mother Mandy Teefey is also said to disapprove of the relationship.