Hall was staying at a hostel on the French Riviera when she was discovered sunbathing on a Saint Tropez beach by a fashion agent, Claude Haddad. She moved to Paris where she shared an apartment with singer Grace Jones (who at that time was also a model) and immersed herself in the Parisian nightlife, often performing risqué cabaret acts in clubs and parties with Jones. Soon after, she moved in with fashion illustrator Antonio Lopez and her modelling career began. In 1975 she appeared, in the guise of a mermaid, on the cover of Roxy Music's album Siren. By 1977, Hall had been on forty magazine covers including Italian Vogue and Cosmopolitan. She was earning modelling fees in excess of $1000 per day.
Her trademark long blonde hair and height of six feet quickly made her one of the most visible and photographed models in the industry during that period. That same year, she met Rolling Stones frontman Mick Jagger at a dinner party in Manhattan, for whom she would eventually leave Bryan Ferry.