Crimes like this don’t often happen on land. A 10-minute slow-motion slaughter captured by a cellphone shows a group of unarmed men at sea, flailing in the water, shot and killed one by one, after which the culprits pose for celebratory selfies. The only thing more shocking than the footage was the government inaction that followed.

The case shows the challenge of prosecuting crimes on the high seas and the reason violence offshore often occurs with impunity. There were at least four ships at the scene that day, but no law required any of the dozens of witnesses to report the killings – and no one did. Authorities learned of the killings only when the video turned up on a cellphone left in a taxi in Fiji in 2014. It’s still unclear who the victims were or why they were shot.

The number of violent killings – and deaths at sea in general – remain extremely hard to assess. The typical estimate has been 32,000 casualties per year, making commercial fishing among the most dangerous professions on the planet. The new estimate is more than 100,000 fatalities per year – more than 300 a day, according to research produced by the FISH Safety Foundation and funded by the Pew Charitable Trusts.

The United Nations, which tracks fatalities by profession, does not indicate how many of these deaths are from avoidable accidents, neglect or violence.

Brutality in distant-water fishing fleets – and the connection to forced labor on these vessels – has been an open secret for a while. A report released in May by the University of Nottingham’s Rights Lab showed, for example, that migrant workers on British fishing ships were systematically overworked and underpaid while more than a third of the workers said they experienced severe physical violence.

Addressing such violence and other brutal conditions in commercial fishing is difficult in large part because so little data is captured or provided to the public.

The case of the murders caught on the cellphone was unusual in that the perpetrator and the ship were eventually identified. A Norwegian research firm that focuses on maritime crime determined the ship was the Taiwanese-flagged Ping Shin 101 by comparing video footage with images in a maritime database. Former deckhands on the Ping Shin were found through Facebook postings where they had discussed their time onboard. Interviews with these former deckhands revealed the name of the captain and details of the killings.

Taiwanese officials, presented with the names of the men and ships in 2015 and 2016, said the victims appeared to be part of a failed pirate attack. But maritime security analysts noted that the claim of piracy has been used to justify violence for a range of offenses, real or otherwise. The victims, they said, might have been crew members who had mutinied, thieves caught stealing or simply rival fishermen. After several years of public pressure, the Taiwanese government issued a warrant for the arrest of the captain of the Ping Shin 101, who ordered the killings. In 2021, he was convicted and sentenced to 26 years in prison.

Such killings will continue to go unchecked without better tracking of offshore violence, more transparency from flag registries and fishing companies, and more effort by governments to prosecute the perpetrators. And that matters because what occurs at sea affects everyone. By some estimates, upwards of 90 percent of world trade is moved by sea.

What can be done? Advocates, law enforcement and researchers suggest four steps.

• Report violence: Human rights researchers suggest that shipowners and crews should be legally obligated to report crimes at sea.

• Regulate registries: Ships on the high seas obey the rules of the countries whose flags they fly.

• Ban transshipment: Forced labor and violent crime is more common on fishing ships that stay at sea longer, something that is enabled by transshipment, in which supply vessels carry catch back to shore so that fishing boats can keep working.
• Monitor employment agencies.

There are reasons for hope. Satellites make it tougher for ships to go dark. Cellphones make it easier for crew members to document violence. Growing use of open-source footage by journalists has bolstered public awareness of human rights and labor abuses offshore. Now, it’s really up to companies and governments to do their part.