Assistant Research Scientist at the Bermuda Biological Station for Research Dr. Dennis Hansell watched as 19-year-old Heather Boswell was attacked by, what is believed to have been, a great white shark in the Pacific Ocean.

Dr. Hansell said all that he and most of the crew could do was watch helplessly as the shocking attack took place.

Ms Boswell is now recovering in hospital in Seattle, her home city, and Dr.

Hansell will visit her on Tuesday.

The attack occurred on Wednesday March 23, about 300 miles off Easter Island off the Chilean coast.

Ms Boswell was part of the crew of the research vessel Discoverer which had recently spent two months off Antarctica. Dr. Hansell was one of the scientists on board studying carbon cycles and global change -- subjects he specialises in at the Bio Station.

Discoverer was heading back to Seattle and Ms Boswell and other crew members were taking a break swimming in the warm South Pacific Ocean.

The shark had appeared "out of nowhere'' and attacked seaman Phil Buffington leaving him with bites to his legs that needed more than 50 stitches.

She heard someone call "shark'' and, said: "I started swimming as fast I could. Then I felt something grab my leg and jerk me. I turned and saw his fin.'' The shark had grabbed her right leg and Ms Boswell stopped moving hoping it would be confused by so many people in the water. She grabbed a stick offered by a crew member in a skiff, but the shark grabbed her left leg and pulled her underwater.

She said: "He was moving his head back and forth, shaking me really hard. I thought I was going to die.'' The shark lifted her back to the surface where she was grabbed by two people in the skiff. A third person was hitting the shark with a stick.

Ms Boswell felt a "popping sensation,'' she said: "I thought it was my hip dislocating but that's when I lost my leg.'' Speaking at the Bio Station, Dr. Hansell said: "I was on deck at the time. We just could not do anything. There was a guy shooting at the shark and a lot of people screaming -- it was a terrible thing.

"To make things worse there were about 30 hours between the attack happening and the girl being airlifted to a hospital in Panama.'' Dr. Hansell added that the whole crew were affected psychologically by the whole incident. He said: "A number of trauma counsellors were flown aboard the ship. The captain was devastated, because he has a daughter around that age. It really hit him.'' Ms Boswell was flown to Seattle last week and is expected to be out of hospital soon. A picture of her appeared in the Seattle Times and Dr. Hansell said: "She looks pretty good in the picture. I will be going to see how she is on Tuesday.

"They are talking about fitting her with a prosthesis, but she has lost her leg pretty high up her thigh.'' In the picture Ms Boswell is seen with a toy shark which her sister bought her to cheer her up.