What changed?

The Marine Accident Investigation Branch (the MAIB, the body that investigates accidents at sea) has published its report into a fatal crash in Portsmouth Harbour, and it comes with a recommendation that would change the law for the rest of us if the government acts on it.

On the evening of 14 August 2025, a RIB called Peaky Blinder hit a navigation beacon at close to 50 knots, roughly five times the 10-knot harbour speed limit. Two people died. Nobody on board was wearing a lifejacket, and the driver had a significant amount of alcohol in his blood.

Off the back of that, the MAIB has recommended that the Secretary of State for Transport switch on alcohol limits for non-professional mariners. The power to do this has sat on the books since the Railways and Transport Safety Act 2003, but the part covering recreational boaters was never brought into force. So right now there is no set drink-drive limit for leisure skippers, even though professional crews have worked to one for years.

The limit being proposed is 50 milligrams of alcohol per 100 millilitres of blood. That is the same limit professional mariners work to, and the same as drink-driving on the roads in Scotland and much of Europe. The road limit in England, Wales, and Northern Ireland is 80 milligrams, so this would be the stricter of the two.

Who does it affect?

If we take a boat out for pleasure, this is aimed at us. The recommendation covers non-professional mariners, so recreational sailors, motor cruisers, RIB and powerboat drivers, and anyone skippering their own boat for fun rather than for work. Commercial crews already sit under alcohol limits, so for them nothing changes.

Nothing has changed in law yet, but it is a pretty strong signal, and it is the second time the MAIB has pushed for this, so it is worth getting our heads around now rather than being caught out later.

What does it mean in practice?

Nothing legally, for the moment. There is no new limit to comply with today.

Alcohol still slows reaction time and clouds judgement, though, and those are the exact things we lean on when a situation on the water changes quickly. Reading a closing bearing, judging a gap, spotting that we are carrying too much speed for the space we are in, all of it gets harder with a few drinks in us. The Portsmouth crash is a hard example of what that looks like when it goes wrong: too fast, in the dark, with no lifejackets, and alcohol in the mix.

What remains uncertain?

Plenty, for now. There is no date for any of this. The MAIB has recommended it, but it is up to the Secretary of State for Transport whether and when to act, and further legislation would then be needed to define exactly which recreational mariners are covered. Small dinghy sailors, paddleboarders, and the like might well be treated differently from someone driving a fast RIB, but that detail has not been written yet.

The enforcement picture is open as well. On the roads the police can breathalyse at the roadside, and how something equivalent would work on the water has not been spelled out.