The spotted eagle ray also died after the impact

Judy Kay Zagorski was boating with her family in the Atlantic Ocean when the 75lb (34kg) spotted eagle ray hit her.

The force of the blow knocked the 57-year-old over and her head struck the deck of the vessel, in what officials called a "bizarre incident".

The ray died in the impact. Mrs Zagorski, of Pigeon, Michigan, was pronounced dead in hospital.

"It's just as freakish an accident as I have heard," wildlife official Jorge Pino told the Associated Press news agency.

The spotted eagle ray resembles a stingray and has a stinging barb at the base of its tail. They are common in warm or tropical waters.

Mr Pino said Zagorski did not appear to have been pierced by a barb.

The incident occurred near the town of Marathon in southern Florida.

In September 2006, Australian TV naturalist Steve Irwin died when a stingray's barb punctured his heart as he filmed at Queensland's Great Barrier Reef.

A month later, an 81-year-old Florida man was lucky to survive after a stingray landed in his boat and left a foot-long barb in his chest.