The black-and-white puppy is then tossed off a rocky cliff.
Whether the 17-second Internet video clip is authentic or a prank, it has drawn sharp condemnation and widespread outrage.
"We're appalled," said Martin Mersereau, spokesman for People for the Ethical Treatment of Animals, or PETA, in Norfolk, Virginia. "Thankfully, it appears the Marines are taking this very seriously, as we expected that they would."
The U.S. Marine Corps is investigating the video, calling it "deplorable and contrary to the high standards we expect of every Marine."
"We do not tolerate this type of behavior and will take appropriate action," it said in a statement.
The alleged name of the Marine who threw the puppy, a 22-year-old lance corporal based at Kaneohe Bay, was uttered in the video and now has been widely circulated on the Internet.
Maj. Chris Perrine, spokesman for the Marine Corps Base Hawaii, earlier said the Marine involved could be based at Kaneohe, but would not confirm his identity.
Perrine was not accepting calls or questions Tuesday, assistant Linda Yokoyama said.
The low-quality video shows two Marines joking before one then hurls the puppy into a rocky gully. A yelping sound is heard as it flips through the air.
Mersereau said an expert with PETA has analyzed the clip frame by frame.
"There are cues in the audio that give us pause, but we have no conclusion, opinion on its validity," he said. "We feel it's absolutely necessary that investigators determine its legitimacy by speaking directly with all those who were involved."
The apparent discrepancy is in the audio of the puppy yelping as it is airborne. Despite the dog moving away from the camera, the sound does not diminish or fade.
"The sound of the puppy screaming doesn't seem to jive with his rapidly increasing distance," said Mersereau, who noted that the group is working with poor quality video from the Internet and not the original tape.
Whether the puppy was dead or alive before it was thrown is also at question.
Mersereau said the puppy being motionless when it was held before the camera does not prove it was dead. Puppies, especially when very young, sometimes go limp when being picked up by the nape, he said.
The Society for the Prevention of Cruelty to Animals International said it was horrified by the acts displayed in the video and hopes the Marine Corps takes "swift and strong action."
Stephanie Scroggs, spokesman for the Washington-based group, said the video was the complete opposite of what she has experienced with U.S. troops. In November, the group launched "Operation Baghdad Pups," helping service members rescue and bring home animals they befriended in Iraq and Afghanistan.
"(They're) desperate to bring them out of that situation and show incredible acts of kindness," she said.
At a cost of $10,000, the group last week helped bring to the U.S. two dogs including a puppy that was found tangled in razor wire during a gunfight in Baghdad. The dog named "K-Pot" was adopted by the family of an Army medic, who treated its wounds.