Greenpeace says it will sink fresh underwater barriers in British Marine Protected Areas. The catching sector has long called the tactic reckless, and the law around it remains unsettled.
Greenpeace UK has announced that it will deploy new underwater boulder barriers in British Marine Protected Areas, reviving a confrontational tactic it last used in 2022. The group says it is acting because successive governments have failed to use post-Brexit powers to shut destructive industrial fishing out of waters that carry a protected designation.
The method is simple and deliberately disruptive. Large inert boulders, granite or limestone, are lowered onto the seabed inside an MPA. Because bottom-towed gear risks snagging or being damaged on the rocks, the barrier is meant to make a patch of seabed effectively off-limits to trawlers. Greenpeace placed boulders at the Dogger Bank MPA in 2020, at Offshore Brighton in 2021, and at the South West Deeps (East) off Cornwall in 2022.
This time the location has not been revealed. The announcement came with a letter to Prime Minister Keir Starmer, signed by conservation bodies including Oceana, the Blue Marine Foundation, the Angling Trust and Rewilding Britain, alongside public figures such as Stephen Fry, Paloma Faith and Simon Pegg. Greenpeace co-executive director Will McCallum said the powers to protect these sites had sat unused for five years, adding: “If this government won’t protect our seas, we will.”
The group’s case rests on the gap between designation and protection. By its own analysis, 1.3 million tonnes of fish have been taken from offshore UK MPAs since 2020, more than a million tonnes of that by pelagic trawlers. It argues that only 17 of the UK’s 78 offshore MPAs carry any protection from industrial fishing at all.
“Catch a large boulder while trawling and there is a risk of overturning the vessel and losing the whole crew.” – NFFO
A reckless tactic, says the industry
The catching sector’s objection has been consistent across every previous drop, and it begins with safety. The National Federation of Fishermen’s Organisations (NFFO) has repeatedly described the barriers as dangerous, illegal and irresponsible. Its then chief executive, Barrie Deas, who retired in 2023, warned that a net snagging a submerged boulder could capsize a vessel and put a crew in the water.
The NFFO’s deeper argument is that fisheries policy should not be written by direct action. In a position piece titled “Lawyers, Boulders and Money”, the federation warned that environmental groups had largely abandoned cooperation in favour of confrontation and litigation, and cautioned about the unintended consequences of pulling blunt legislative levers without engaging the people affected. It has also pushed back on what it calls a catastrophe narrative, noting that most stocks have been moving in the right direction for the best part of two decades.
There is a further point the sector makes about who actually works these grounds. At South West Deeps, the Marine Management Organisation recorded that the vessels fishing the area were predominantly French and Spanish, with only two UK static netters among them. A barrier framed as protecting British waters can, in practice, fall hardest on EU boats operating under agreed access arrangements, which complicates the politics considerably.
The law remains unsettled
This is where the story is heats up, because the legal position has never been cleanly resolved. Depositing material onto the seabed below the high-water mark generally requires a marine licence under the Marine and Coastal Access Act 2009. Greenpeace has never held or applied for one, and when it acted at South West Deeps the MMO stated that the activity was potentially illegal and opened a formal investigation.
The one prosecution that reached court did not end well for the regulator. The MMO took Greenpeace and its then director John Sauven to court over the Brighton drop. At Newcastle Crown Court in January 2022, Judge Edward Bindloss ruled on the points of law in the MMO’s favour, finding the court had jurisdiction and that the case could proceed to trial. But he also observed that it touched on the absurd that the litigation was happening at all, and suggested the two parties should be allies rather than antagonists. He found the boulders were not harmful and that Greenpeace’s actions were not dangerous, partly because coordinates had been published and the rocks could be lifted off again. The MMO then dropped the case, offering no evidence.
That outcome left an awkward settlement. The MMO maintains that the ruling confirmed its jurisdiction to prosecute unlicensed activity, and that Greenpeace is expected to comply with the licensing regime. Yet the only test case collapsed, and the judge’s finding that the barriers were neither harmful nor dangerous sits directly against the safety argument the industry puts at the centre of its objection.
A ban that stopped short
The new action lands against a specific policy backdrop. In June 2025 Defra and the MMO opened a consultation proposing to ban bottom-towed gear across 41 offshore MPAs, covering roughly 30,000 square kilometres, on top of the 18,000 square kilometres of English seabed already closed to such gear. But in its September 2025 response to the Environmental Audit Committee, the government ruled out whole-site bans, calling blanket closures disproportionate and not in line with legislation, and confirming a feature-based approach that restricts fishing only where it is assessed to damage the specific features a site was designated to protect.
For Greenpeace, that half-measure is the trigger. For the catching sector, the feature-based model is the proportionate one, and the prospect of further unlicensed boulder drops, in grounds worked largely by legitimate licensed vessels, reopens a fight the industry believed the courts had already exposed as absurd. With the locations still to be named, the fleet will be watching the water.
