The whale, an ailing endangered finback stretching about 60 feet long, apparently beached itself at Beach 216th Street and Palmer Place at around 10:40 a.m.
The whale was still alive when it washed ashore, and first responders were spraying water on it while wildlife officials evaluated the situation.
Officials from the Riverhead Foundation determined they couldn't do anything for the whale and would let it die a natural death.
Their rescue coordinator said it would be inhumane to move the whale, which later drifted away at high tide and washed ashore again Thursday morning, this time dead.
The whale was severely emaciated and in very bad shape. Biologist Mendy Garron said the whale wasn't moving around much and "looked very compromised."
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