Millions of containers are shipped around the world. Helen Fretter investigates what the chances of hitting one at sea really are.


It is the stuff of every sailor’s nightmare – the unseen object, lurking beneath a wave, which punctures your hull or smashes your rudder mid-ocean. Never have our oceans seemed so crowded – last year’s Vendée Globe was peppered with reports of single-handed racers smashing into ‘UFO’s (unidentified floating objects), often at high speed, in remote regions, with devastating effects.

But do containers represent a genuine hazard? There is an acute awareness of the impact debris has on the marine environment, yet an apparent lack of current data on how many containers fall overboard – and what happens to them when they do.

There is no requirement for shipping lines to sink, track or retrieve containers lost offshore, so their positions are almost entirely unknown. Sailors who suffer a mid-ocean impact usually have little evidence of what they hit.

The risk may be minuscule, but it is almost impossible to quantify.

‘Like a car accident’

Mike Sargeant was delivering a Farr 52 from the UK to Las Palmas via Cascais last autumn when they collided with something that damaged the yacht’s 3.6m draught keel.

“We were probably about two days out of Las Palmas,” Sargeant recalls. “We had good winds, and it was about 0130, pitch black around 400 miles off Madeira.

“We were doing about 8 knots, which was quite slow really – we had been surfing at around 17-18 knots. I was helming on the port wheel, and it was like a car accident.

“The yacht just went BOOM, and stopped dead. The collision basically threw me off the wheel, it broke one of the spokes of the carbon wheel, and it threw everyone onto the deck.

“We all picked ourselves up quickly and looked at each other. The skipper was shouting, ‘Have you got steerage? Have you got steerage?’.

“I had nothing, but we weren’t moving. We checked the boat from bow to stern. We couldn’t see any leaks  – mind you, the Farr 52’s a pretty wet boat anyway.

“Everyone was pulling up sole boards and running through launching the liferafts. Once it was obvious we were steering straight with no apparent damage to the rudder we continued on our way.”

Sargeant says the boat stopped dead before seeming to roll over something on a wave.

“When we got to Las Palmas as soon as we could we sent divers down and they photographed the keel. The bulb is 3.6m below the water level and it had taken a big chunk out of the keel, trashed all of the leading edge and cracked the hull as well.”

Was it a container they collided with?

Sargeant feels all the evidence points to that: “It was something hard and it had given us a huge hit. We were sailing in a high traffic area, and had seen plenty of container ships out there.”

G1K086 Cargo ship sail to Miami port, Florida, USA

How many shipping containers are lost at sea each year?

Almost everything you see, are wearing, or have eaten recently, was transported in a shipping container at some stage. Ninety per cent of goods traded around the world are shipped on the oceans, and there are around 5-6 million containers at sea at any one time.

Yet finding reliable data on how many containers actually fall overboard is a challenge. The widely quoted figure of 10,000 containers lost every year [1] was the basis for reports by organisations ranging from Friends of the Earth to the US Congress. But the World Shipping Council (WSC), a trade body that represents 90 per cent of the global shipping industry, disputes that number [2].

Based on surveys of its members the WSC reported that for the years 2011, 2012, and 2013 there were around 2,683 containers lost each year [3]. Combining that data with surveys going back to 2008, the WSC reports that excluding ‘catastrophic events’ the number of containers lost every year is a mere 546.

However, the data is several years old, and based on voluntary responses, so can it be relied upon?

“Bearing in mind the volume of shipping going on these days, and the accountability of shipping from an environmental impact, if there was more than this going on in the industry we’d know about it,” comments Jonathan Ridley, head of engineering at Southampton Solent University, who is an authority on the industry.

“It’s pretty obvious when a ship arrives in port if containers are damaged or missing, or there’s a stack leaning over. It’s a reportable event.

“If there is an accident with material damage to the ship or pollution the Master and owner have to report the accident for investigation, so I feel quite confident that that’s a realistic figure.”

The littered ocean

However, the stakes are rising. The global shipping industry was hit hard by the 2008 economic crash. In the search for profitability, many lines have launched larger, slower ships – at this scale the cost savings on fuel for running just a few knots slower can be immense.

Now, following the extension of the Panama Canal last year, the latest generation ‘neo-Panamax’ ships have a 49m beam and can bear a vast load of around 9,600 40ft containers.

In 2013 the MOL Comfort broke up in the Indian Ocean, shedding just under 4,300 containers, the biggest single loss ever. As even larger, slower ships carry more containers for longer, potentially making them more vulnerable to storms, a ‘catastrophic event’ could see more than twice that number of metal boxes and their contents released in a single incident.

A major loss in 2014 highlighted just how many containers may already dot the seabed. On 14 February the Svendborg Maersk lost 517 units off Ushant.

Unusually, the French authorities requested Maersk to locate all of the containers.

“They did this unilaterally, and it went way beyond what the IMO expects,” explains Toby Priestly, who has designed a device to sink containers that fall overboard. “They said, ‘We have fishermen in these waters dragging nets along and we need you to plot where every single one of these containers is.’

“So suddenly there was a liability attached.”

Using the same weather modelling software as the Maritime and Coastguard Agency, Priestly plotted the current and weather conditions in the area at the time for 96 hours (at least one container was beached 96 hours after it was lost). This gave a search area of over 9,000 square nautical miles.

Maersk chartered a side-facing sonar ship, and within just a few months reported that it had located some 500 containers.

“Or at least, they found over 500 containers in the area which they searched, which is one of the busiest shipping lanes on the planet,” explains Priestly.

With no way of identifying the source of each container, Priestly points out, there is no way of knowing whether they were the same units which fell from the Svendborg Maersk, or simply indicative of how many containers litter the Channel.  Around a dozen containers were also found floating in the weeks following.

Almost all containers that go overboard will sink – eventually.

“They could sink within days, or they could be several months still afloat, it depends on the type,” comments Solent University’s Jonathan Ridley.

“All have doors with rubber seals and when their rubber seals start to break down you’re going to get water in. The containers’ major structure is in their corners – the side panels have a minimum thickness of 1.6mm, which is not a lot for steel.

“So if a container falls off the side of a vessel the twisting torsion on it is probably enough that the container would fail.”

He adds that a loaded container with moving cargo inside is likely to suffer a loss of structural integrity fairly quickly in waves.

Refrigerated containers, known as ‘reefers’, are tightly sealed, insulated units used to transport perishable food, and are likely to float for months. Meanwhile, if the door seals are unbroken, containers carrying light, high value cargo such as smartphones, each wrapped in protective layers of Styrofoam and inflatable packaging, could potentially float indefinitely.

One myth Priestly debunks is the notion that containers can float just below the sea’s surface.

“I did a lot of tank tests on this, and that is actually physically impossible. It might be that a wave washes over it, and it can float very low in the water, but once a container actually goes beneath the surface of the sea, the air inside the container gradually gets compressed and gets less buoyant, so it sinks.

“But it could be just a couple of inches above the surface, and if it’s filled with the right amount of polystyrene, it could stay there forever. “

Exaggerated risk

So how likely are you to encounter one? The spate of collisions reported by competitors in the Vendée Globe focussed the mind of many sailors on the unseen dangers apparently lurking.

Only one competitor reported a suspected collision with a shipping container, with Thomas Ruyant’s Le Souffle du Nord pour Le Projet Imagine cracking around him after what Ruyant reported as “an exceptionally violent” bang, some 250 miles south of New Zealand.

We contacted his team to see if they had been able to learn more about the impact, but were unable to get a response.

At the speeds racing yachts now travel, a crash into a marine mammal can cause a catastrophic impact which has all the violence of hitting a lump of steel, as Kito de Pavant’s onboard video from his collision with a sperm whale in the Vendée shows.

Fin whale.

Guillaume Evrard, deputy race director for the last edition of the Vendée Globe, says that race organisation teams rely on MRCCs to report any hazards on the course. In around a decade of working on race organisation, he has never received a warning of any shipping containers on the route.

Organisers of the Clipper Round the World Yacht Race which has seen more than 4,000 people compete in ocean stages, say none of their boats has ever had a close encounter with one – the nearest being in 2012, when the fleet was diverted after a container ship hit a reef off New Zealand.

World Cruising Club reports that in 30 years of transatlantic rallies and other events, with more than 200 boats crossing the Atlantic each year, there have been no confirmed incidents of a yacht colliding with a container.

Mike Golding, who has sailed some 250,000 ocean miles, admits to being ‘a little bit of a sceptic’ about the many collisions with both debris and mammals reported in solo races, pointing out that an insurance claim for a collision can be the most expedient way of dealing with a breakage situation. While he has sighted everything from fridges and tables to fishing gear and logs on his many ocean crossings, he has never spotted a container.

“I think the ocean is very, very large, we tend to forget how vast it is when you’re looking at your triangle on MaxSea, but the reality is you are a pixel in this huge area.”

But they are out there.

Containers can be stacked in blocks of nine or more units high, and are secured together using a twist-lock system, with the lower units lashed to the deck or lashing bridge. The main causes of containers toppling overboard are when the twist-locks or lashings fail, the stack is unbalanced, the ship is hit by storm conditions, or a combination of these factors.

Loading a container ship is a fine art: it must not be overly loaded at either end (which can cause ships to buckle in large waves), and with any potentially dangerous cargo stowed away from other hazards or accommodation. It’s rare an entire ship is unloaded in a single stop so the right containers need to be accessible at each port. The logistics and ground crews can only achieve this if the cargo and weight of each container is accurately known.

In 2007 the MSC Napoli was grounded off Devon in 2007, shedding around 600 containers into the English Channel. Around a fifth of the containers on board were found to be heavier than their records declared, and some 53 per cent were loaded in a different or incorrect position [4].

A container from MSC Napoli off the coast of Devon.

Since 2015 the industry has put a big emphasis on accurate weighing of each container. “It used to be that the shipping company’s customer declared the weight of the container contents, and from their point of view they make money by moving as much cargo as possible at once,” explains Jonathan Ridley of Southampton Solent University.

“So if you are self-declaring the weight there is a potential gain there. Now a shipper has to declare the weight of the container, either by weighing individual contents or by using a weigh-bridge.

“Each container has to have a stated weight – known as the verified gross mass – and if it doesn’t then it doesn’t get shipped. If you don’t know the weight of your container you don’t know the loads on it, so [now] there’s much better confidence in each individual stack’s ability to support its own weight.”

In the 2015 Transatlantic Race the 100ft maxi Nomad IV had a close encounter.

Skipper Clarke Murphy reported: “I was at the wheel in pea-soup fog, no visibility, going 15 knots. All of a sudden I see, ten metres off the bow, a huge breaching whale and I scream ‘Whale!’ — I have hit whales before in previous trips.

“So I shoved the wheel to windward and we passed two to three metres by a floating 40ft container covered in barnacles on the port side. We were so close, you could see its registration number.”

Cruising sailors have also reported collisions and near-misses. Paul Lutus cruised around the world solo in his 31-footer Selene.

Lutus, a prize-winning scientist who has designed component parts for NASA space shuttles, is not the type to make hyperbolic claims without evidence, but is confident he collided with a container in 1990.

“I remember smacking something very hard one night in the Indian Ocean. I was nearly thrown from my sleeping berth, items went flying inside the boat, and the sound was unmistakably that of a large solid object, unlike the many nearly-waterlogged trees (and one whale) with which I had collided over the years.

“With the boat out of the water I could see three large cracks radiating from the impact point to about eight inches, and a pattern of oval concentric cracks in the paint showed that the entire hull had flexed at the impact.

“The scar the container left in the hull added to my certainty – it was a three-sided indentation, such as one would get from pressing the corner of a cube into a solid surface. The only reason I didn’t have to take to my lifeboat was because my hull’s thickness was three inches at the collision point.”

Selene was a Pacific Seacraft Mariah 31, renowned for their exceptionally robust construction.

Whether it’s a container, log, fishing gear or other detritus, hitting a floating object mid-ocean can quickly escalate into a critical situation.

John Jennings was sailing his Catalina 41 Coolabah with his wife and sons from Samoa to Suva, Fiji in 2008, when the boat impacted something – he believes a container – sharp enough to puncture the hull.

“Ten or 15 minutes after that, the floorboards started floating,” Jennings recalls. “I told my son Harry to check the integrity of the through-hulls and seacocks in the aft of the vessel while I checked forward.”

“I opened all cupboards and compartments to try to find the source of water ingress. I started removing as much material as I could to gain further access but the water level was rising uncomfortably quickly.”

The family made preparations to launch the liferaft.

Coolabah sinking in the Pacific.

“When the water was so deep that the auto-inflate device on my life jacket actuated I decided that I would finally abandon Coolabah,” Jennings recalls. Fortunately they were sailing in company with another yacht, which reached them within an hour of being radioed, and the family evacuated to their companion before watching Coolabah sink.

The Catalina remained vertical throughout, with her keel and rudder apparently intact.

What are the solutions?

Jonathan Ridley says the industry’s focus has been on improved seakeeping design of the ships, which should help prevent containers from toppling [5].

“In the last 20 years there’s been a big drive in the shape of container ships to increase the deck space on board. Much larger deck space means a more flared bow and overhanging stern, and a flared bow and overhanging stern has introduced a particular problem called parametric roll where the roll motion of the vessel can get exaggerated.

“So a lot of shipping companies are doing significant work to say if you are in waves of this frequency this is the heading and speed you should maintain to keep that to a minimum.”

Toby Priestly’s Containersinka will scuttle an empty container in under six hours so it no longer presents a hazard to shipping, although from an environmental perspective condemning the unit and its contents to the seabed is an imperfect solution.

“The device is basically a combination of an air pocket and a ‘U-bend’,” Priestly explains.

“The brief from Maersk was that it had to withstand 10-15 seconds of immersion. The design is a tube that is completely open but it won’t let water through for 30 seconds, so if a wave breaks over the bow of a ship it won’t let water into the container before the water subsides. But if it’s in the open ocean then after 30 seconds water starts flooding in through a tube.”

A single device costs around US$1 and four (the number needed to guarantee an empty 40ft container will sink [6]) can be retrofitted for less than $10. It has received praise from the industry, but is yet to be adopted by any line.

Andrew Pindar of GAC, a company that provides auxiliary shipping and logistics services but also works closely with ocean racing organisers and teams, believes more action is needed.

“Certainly there is something that needs to be done in our opinion by the world shipping industry to address the problem, in terms of the pollution problem and also as a safety issue. We’ve been looking into how you could identify containers that have come off vessels, and at technologies that might be appropriate.

“Something like an RDF (radio direction finder) or some kind of automated beacon that is set off – there has to be a way but of the things we’ve looked at so far nothing would relieve the problem. It’s going to take further testing and development.”

Our verdict

It is hard not to be sceptical of industry claims that just 500-odd containers routinely fall into the sea every year when such vast numbers are moving around the world every day. If container losses are reportable, why does every industry body we asked refer to the same, three-year-old survey – is there really no more current data?

What, possibly, could this billion-dollar industry have to hide? We approached market leaders Maersk and the WSC, but received no response. Any doubts are exacerbated when a race like the Vendée Globe gives the impression our oceans are littered with obstacles.

But if container losses rank in the tens of thousands each year, why are there so few recorded incidents or verified sightings? Most tellingly of all, none of the marine insurance companies we spoke to could recall handling a claim for a yacht that had hit a container.

Containers are out there, they can float, but the likelihood of colliding with one is vanishingly small.

That’s not to say improvements cannot and should not be made. There has never been greater focus on marine environmental issues, with countries as varied as Rwanda and India passing legislation banning types of plastic packaging to protect ocean life, so it seems nonsensical that shipping lines can routinely drop hundreds, if not thousands, of containers into the sea with little or no consequence.

Without financial liability for losses, there is no incentive for shipping lines to invest in new technology. And it is technology – whether that be robust container tracking, or forward-facing sonars on yachts, or some other solution – which will ultimately make collision avoidance more than a matter of chance.