A navy ship has rescued a woman after a suspected shark attack about 10 hours off the coast of Mackay in north Queensland.

The Queensland Ambulance Service (QAS) says the woman, aged in her 50s, was snorkelling on Wednesday afternoon when she was bitten by a shark and returned to her boat.

The QAS was alerted by the Department of Defence about 4:30pm.

HMAS Warramunga, which was in the Whitsundays region for training exercises, diverted from its path to pick up the woman.

Navy staff onboard applied a tourniquet and transported her to the mainland, arriving in Mackay Harbour about 12:30am this morning, when the ship was met with awaiting paramedics.

The Mackay Hospital and Health Service said the woman was treated for cuts to her leg after a suspected shark bite, and was in a stable condition