A woman who was attacked by a shark on a West Australian reef says all she could think of was fighting it off before it could savage her teenage son wading alongside or the 3-year-old on her hip.

Mother-of-five Becky Cooke, 38, had her heel and calf lacerated by the 2.5 meter shark as she waded across a coral reef with two of her sons at remote Warra Beach, south of Coral Bay, on Wednesday.

From her bed in Royal Perth Hospital Friday she described how scared she had been when she realized she had been bitten and more sharks could be attracted by her spreading blood.

"All I could think of was getting it off my leg so I could get to shore because I did not know if it was alone, or if there were others sharks out there," Cooke said.

Water turned red

Flanked by her husband Peter and sons, Brandon, 13, Hayden, 10, Jacob, 7, James, 6, and Ethan, 3, Cooke explained she had been wading in shallow water with Ethan and Brandon when the shark struck on day four of their nine-day holiday.

"It just felt like something had hit me, at first, I turned around and I saw all this thrashing and the water just turned red.

"My son was with me, we were walking together, I just think thank goodness it bit me, not Brandon.

"I had my camera in my hand and Ethan on my hip, I started hitting it with my camera and shaking my leg trying to get it off.

"It let go, I took a couple of steps and fell into the water because my leg was pretty bad.

"As I fell into the water the sea just turned to blood.

"It was pretty scary, I wasn't sure if it had gone, if it was going to come back."

Worried for children

Cooke said her main worry was the unidentified shark might attack her children.

"Brandon came running over and I said to him 'take Ethan' and he grabbed Ethan and ran back to shore."

She said she did not feel the pain until she reached the shore where she was given first aid, helped by her husband, family friends and two volunteer conservation officers who turned up at the beach just moments before the attack.

Cooke said he used his mobile to call for help and then drove his wife in their four-wheel-drive to Coral Bay where she was taken by ambulance to Carnarvon and on to Perth.

She will have an operation tonight on her severe calf wounds, knowing she could face two years of treatment.

"I could still lose my foot, I would like to try and save my foot," she said.