The common dolphin was five-feet long and weighed about 200 pounds.
A police officer responded after a jogger noticed the mammal on the sand around 7:30 a.m.
The officer and a volunteer from the Marine Mammal Stranding Center poured buckets of water on the dolphin, but it died at 9:10 a.m.
It was the eighth dolphin to die on the beaches of New Jersey this month, said Bob Schoelkopf, director of the stranding center.
He said there were no obvious causes for the deaths, which may just be natural occurrences.
"It's a higher number than we usually see, but there's no one thing that we're concerned about at this point," he said. "It could just be indicative of a high number of dolphins offshore right now."
Ruth Reese, who lives nearby, said she saw a large group of dolphins jumping and splashing in the water off the 85th Street beach on Monday. That's where the dying dolphin washed up Tuesday morning.
"It's very sad," she said.
Rana Schaefer, a volunteer with the stranding center, covered the dolphin with a red and black striped blanket and kept pouring small buckets of water over it to help it breathe while waiting for the center's truck to come and possibly take it back to their headquarters for emergency treatment.
But the already weakened dolphin, which had been meekly thrashing on the sand, digging a shallow hole with its tail as it struggled, stopped breathing just minutes before the truck arrived.