Three men who viciously attacked a protected leopard seal by throwing rocks at it and dragging it down a beach were undone by placing their photos on Facebook.

Michael William Mathews, 23, Harley David McKenzie, 20, and Phillip Ray Horrell, 24, appeared before Judge Jane Farish in the Invercargill District Court yesterday charged with taking a leopard seal and injuring it on or about October 27.

The attack, which happened near Rowellan Burn, at Te Waewae Bay, and carries a maximum penalty of six months in jail or a $250,000 fine, was detailed by Department of Conservation principal compliance officer Alan Christie.

Mr Christie told the court the three men, all shearers of Tuatapere, were driving past the beach when they spotted the seal and stopped to get a closer look.

Horrell filmed the seal while the two others forcefully threw rocks the size of fists at it to try to antagonise it into chasing them, he said.

Rocks struck the seal multiple times, including at least twice in the head, and the seal appeared to lose consciousness at one stage, he said.

After stopping the filming Horrell and McKenzie then dragged the injured seal down the beach, before pictures were taken of two of the men posing beside it with wide smiles and thumbs up, he said.

The photos were placed in a file titled "Good Times" by Horrell and then uploaded to Facebook, which attracted DOC's attention, Mr Christie said.

Horrell's lawyer Bill Dawkins said Horrell did not participate in the actions as much as the other men and could be heard at the time telling them to stop.

However, Judge Farish said Horrell was more worried about his personal safety than harming the seal and during the video he could be heard laughing and saying "It's f-ed already" and "It's really f-ed now".

Horrell was getting "his kicks loading it on to his Facebook page" and the actions of all three men were appalling and barbaric, Judge Farish said. "The animal was clearly distressed.

"You didn't show any humanity to the animal on that afternoon.

"It was a barbaric act."

Matthews' lawyer Richard Smith told the court Matthews said it was "the dumbest thing I have ever done and really regret it".

Horrell was fined $5000 and Matthews was find $7000.

McKenzie, who has a previous conviction for animal cruelty, was remanded to November 12 for sentence.

Judge Farish said if the leopard seal had died then she would have had no qualms with sending all three men to jail.