The clip was posted on YouTube by Sean Donohue, who said he witnessed the encounter near 106th Street Beach in Long Beach Township.
There were unconfirmed reports that the dolphin was injured by a boat propeller and the blood in the water caused the sharks to attack.
Long Beach Township Police Captain Kevin Mahon confirmed with TAPinto that this encounter did take place and that more than one shark was spotted Thursday morning.
Mahon was not immediately available for comment on Friday.
According to shark expert Stephen Kajiura, dolphins and sharks generally swim side by side "minding their own business," he told Live Science.
More aggressive dolphins will sometimes antagonize sharks if they feel threatened, ramming the sharks with their noses or body slamming them, Kajiura said.
The face-offs are rare, the expert said.
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