"In the old days it wasn't unusual, about 20 to 25 years ago, but these days it is very unusual, in fact I am quite excited about it because they have quite an important part to play in the marine ecosystem."
He said experienced divers and underwater photographers had techniques to deal with such close encounters.
"We are very respectful of them and we are very careful and have techniques. We have little baskets we can dip into and push them off, we are pushing them off all the time.
"I don't like to encourage people to do it because you have to know what you're doing."
The pair also saw a sizeable pod of young common dolphins, and a number of albatrosses.
A 118kg thresher shark and 128kg striped marlin were also caught during the Coruba Fishing Competition.
However, the divers' subjects were among the most outstanding of the summer, according to experts.
Mr Duffy said sharks did not pose a high risk to water users.
Sharks in HB waters
Blue sharks and mako sharks are most common in Hawke's Bay waters during summer months. Sometimes there can also be large hammerheads and bronze whalers, with the occasional great white shark.
Mako sharks in Hawke's Bay are some of the biggest in the world, reaching lengths of up to 3.7m and weighing up to 415kg. Blue sharks in Hawke's Bay reach up to 3.3m and weigh about 110kg, bronze whalers are the same lengths but weigh between 180kg and 280kg.
Hammerheads in our waters weigh around 100kg to 120kg and are about 2.8m to 3m in length, and great whites range from 1.5m to 1.8m, with fully grown sharks measuring up to 4m.
New Zealand's most recent fatal attack occurred in 1976, near the Bay of Plenty, when a spearfisherman was attacked by a bronze whaler as he was lifting a fish into a boat.
Hawke's Bay's last victim of a confirmed fatal shark attack was 26-year old Napier man Bright Cooper, who was killed while swimming off Marine Parade in 1886.