"It was a little bit gross," Mr Messenger told AAP.
"It was like a big pile of jelly, like a big blob. You can't see the head or the tail."
The ocean pool that the whale washed into, crushing the bollards and chains around it, has been closed off as rangers decide how to remove the dead mammal.
A sign erected by the council also says the beach has been closed, warning of a possible increase in shark activity.
"Whenever you get a dead whale, there's a chance of pieces of dead whale, blubber or oil washed out there, and that will attract sharks," NPWS northern beaches manager Chris Grudnoff said.
"A whale like this would be a very good feed for a pack of sharks."
The situation would be reassessed after low tide, Mr Grudnoff said, but it could take two days to get rid of the whale.
A tugboat or a 20-tonne excavator could be used to remove it, or authorities would wait for the 1.9 metre swell expected on Wednesday night to wash it out of the ocean pool.
"We will be possibly be leaving it up to nature after our assessment at low tide," Mr Grudnoff said.
One of the problems associated with the carcass was the strong and repulsive smell at the beach, he said.
The NSW Environment Department later said on its Twitter feed that the whale is believed to have died in the last two days.
There was no evidence of boat strike or entanglement, it said, although the whale seemed to have suffered some shark bites after its death.
- AAP
