Pete Holm was fishing in his runabout with his son, Luke, 7, about 10.45am when he saw Steven Fogarty, 24, waving his arms and thrashing in the water about 40m offshore beneath the Windang Bridge.

Mr Holm, of Koonawarra, didn't hesitate, rushing to Mr Fogarty's aid and dragging him aboard.

"I don't think I am a hero; I just did what anyone would," Mr Holm told the Mercury yesterday.

"(Mr Fogarty) was more shocked than anything; he said only that he thought something had bit his leg but he didn't know what it was.

"It's not hard to tell it's a shark bite - it's a fair size and you could see the teeth marks."

Mr Holm brought Mr Fogarty to safety on the northern bank of Lake Illawarra, east of Windang Bridge. There, waiting ambulance paramedics treated Mr Fogarty for 40 puncture wounds to his right calf and abrasions to his right fist. He was taken to Shellharbour Hospital in a stable condition and later released.

Mr Fogarty's family arrived at the scene when they heard news of the attack.

"When I heard, I knew it was him," Mr Fogarty's aunt, Joan Baldwin, said.

Mrs Baldwin said Mr Fogarty had snorkelled in the area for years and she often allowed her 10-year-old grandson, Rhys, to accompany him.

"He usually took my grandson with him, but Rhys is in Sydney at the moment so that was lucky," Mrs Baldwin said.

She said it was fortunate the shark had taken no flesh and left only bite marks.

"He is lucky it didn't take a chunk out."

An ambulance spokeswoman said Mr Fogarty was looking at a shoal of fish when he felt a tug on his right leg.

"He observed a brown shadow near his leg and punched at it, causing it to release its grip," the spokeswoman said. "The shark is believed to be a bull shark, several of which have been sighted recently as they make their way into the lake in search of bait fish."