McGill, along with Dawn Fraser, was banned by the amateur swimming authorities as punishment for alleged misbehavior at 1964 Tokyo Olympic Games where she swam 4 events. Five months after being suspended, she became the first Australian to swim the English Channel in 1965 (11 hours 12 minutes from France-to-England). In 1967, she set a women's record for the swim of 9 hours 59 minutes 57 seconds, a time that came very close to beating the men's record (9 hours 35 minutes). Her record swim on her third English Channel attempt came after an earlier 13 hour 2 minute crossing. Three months later, she became the first person to swim across Port Phillip Bay in Victoria, Australia when she swam 25 miles from Portarlington to Frankston in 13 hours, the first person to swim around Hong Kong Island, and from Townsville to Magnetic Island, Queensland, Australia. In 1977 at the age of 32, she became the first person to swim across the Arabian Gulf non-stop and in 1968 she swam in 29km race from Capri to Naples in Italy in 9 hours 52 minutes to finish as the first woman, but was disqualified because her guide became seasick and returned to shore.
She wrote an autobiography called Surviving the Sea of Life: The Triumphs and Tragedies of an Australian Olympian. The 256-page book covers McGill's life, an inspiring victory against fate: surviving her mother's tragic death, a scandalous ban from the Tokyo Olympics along with Dawn Fraser, a near-fatal car accident and a devastating divorce. Then there are the triumphs, including claiming the title as the first Australian to swim the English Channel, record-breaking marathon swims and the honour of an MBE. At times funny and always entertaining, she describes in detail her life with her close friends and swimming legends Don Talbot, Dawn Fraser and Ilsa Konrad. She writes about her world travels meeting the rich and famous, sportstars, filmstars, politicians and millionaires. The final chapter deals with her latest battle against the skin cancer borne from a life lived in the water, in an age unaware of the dangers of sun exposure.
- 1962 Gold Medalist at Perth Empire and Commonwealth Games - Swimming - 4 x 110y Medley relay
- 1965 First Australian to swim the English Channel
- 1967 Broke the women's record for the English Channel
- 1968 First Australian to swim across Port Phillip Bay