NYPD officers rushed to the washed-up dolphin near Beach 19th Street.
The officers poured water on the mammal, and its tiny fin started flapping.
Animal rescuers from the Riverhead Foundation responded to the scene just after 12:30.
The dolphin was taken to a Long Island facility for treatment, where it later died, during attempts to save it.
A necropsy will determine the exact cause of death cause of death.
Rescuers said she was a six foot long female common dolphin. She was underweight, indicating she had been sick for a while.
Rescuers credit witnesses for calling immediately and staying back from the dolphin, making their rescue attempts easier.
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