The 45-second video shows the shark circling with what an observer calls "a big flathead in his mouth".

It has what the Department of Primary Industries calls the "extremely tall, sickle shaped" main dorsal fin and the long raked tail of a great hammerhead (Sphyrna makarran).

The video was shot on January 3 in waters off Shingle Splitters Point, not far from the Yarrawonga Park shore where Mr Burbury was bitten on the arm on Saturday evening.

"He's pretty big," one of the young men in the craft says, as they steer around the shark, with the two tall stacks of Eraring Power Station clearly visible at one point.

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Mr Burbury remained in John Hunter Hospital yesterday in a stable condition, with hospital spokespeople saying that neither he nor his wife, Dr Julie Kibby, wished to comment about the attack.

Neighbours who came to their aid on Saturday before the ambulances and paramedics arrived said the couple had come to swim at the reserve in front of where they had previously lived.

Eye-witnesses said the injuries to Mr Burbury's arm were very deep with "flesh and muscle hanging everywhere" below his elbow. The DPI said yesterday it believed a bull shark of indeterminate size was responsible.

Ambulance inspector Grahame Rathbone praised all those who helped at the shore and thanked Dr Kibby for her efforts in explaining her husband's medical history to the paramedics.

Mr Burbury has been described as a marine biologist.

Sarah Laverick, whose book Through Ice and Fire chronicled the 30-year history of the Newcastle-built icebreaker Aurora Australis, said Mr Burbury had made many voyages to Antarctica with the Australian Antarctic Division and was on the Australis's maiden voyage.

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