chris blowes is in a critical condition after a shark attack in south australia .
police said the 26-year-old was attacked 350m offshore at fishery bay .
he is in a critical condition in intensive care at royal adelaide hospital .
the attack by a great white shark happened just before 10 am on saturday .
witnesses claim the predator bit off the man 's leg and swam away with it .
his family released a statement thanking for the support and well wishes .
south australia has been the site of numerous shark attacks .