The animal - part of an endangered species known as finback or fin whales - was severely emaciated but clinging to life when it was discovered Wednesday stranded on the bay side of Breezy Point. Volunteer firefighters sprayed water on the whale as it sat halfway out of the water.
At high tide, the whale drifted away and out of sight before washing ashore again on Thursday morning, this time having stopped breathing, said Mendy Garron of the National Marine Fisheries Service.
Marine experts later confirmed the animal was dead. They planned to perform a necropsy to determine a cause of death before burying the giant carcass, said Kimberly Durham of the Riverhead Foundation for Marine Research.
The experts had given little hope the whale would survive because it appeared to weigh only about 20 to 30 tons - well less than half normal. The whale appeared to have scratches or streaks of blood on its body, but no signs of serious trauma suggesting it had been hit by a boat.
According to the state Department of Environmental Conservation, finbacks average 70 feet in length and 70 tons in weight - second in size only to blue whales. It also is one of nature's fastest whales, capable of short bursts of up to 35 mph.
The whales were placed on the endangered species list after whaling decimated their numbers in the North Atlantic before a 1987 ban. Some estimates put their current count in the North Atlantic below 2,000.
Experts say the biggest threats to the finbacks are collisions with large ships, entanglement with fishing gear and a depletion of food supply because of overfishing.
Superstorm Sandy caused serious flooding and a fire that destroyed 100 homes in Breezy Point when it struck in October.