Rescue authorities say the man was bitten repeatedly last night at the Del Rio water ski resort at Wisemans Ferry, in Sydney's outer north-west.
He was attacked when he picked up the Death Adder in the dark, thinking it was a lizard.
Other holiday makers killed the snake and put it in a plastic bag so it could be positively identified by hospital staff.
The man suffered a heart attack and paralysis a helicopter trauma team revived him and worked for 30 minutes to stabilise him before placing him on the helicopter's ventilator and flying him to Westmead hospital.
He arrived at late last night and was given two doses of
anti-venom -- he's expected to receive more doses today.
He is listed as being in a stable condition but remains in the intensive care unit.