A surfer mauled by a shark in northern New South Wales two days ago has woken from a medically induced coma.

Sam Morgan, 20, underwent surgery and was put in an induced coma at the Gold Coast University Hospital after being bitten by a bull shark at Ballina on Tuesday evening.

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A hospital spokesman said Mr Morgan was in a stable condition and doing well.

Mr Morgan was surfing on his own at Lighthouse Beach at about 6:30pm when he was bitten on the left thigh.

He made his own way out of the water before being helped by beachgoers until paramedics arrived and he was flown to hospital.