The world's cargo ships are getting big, really big. No surprise, perhaps, given the volume of goods produced in Asia and consumed in Europe and the US. But are these giant symbols of the world's trade imbalance growing beyond all reason?
What is blue, a quarter of a mile long, and taller than London's Olympic stadium?
The answer - this year's new class of container ship, the Triple E. When it goes into service this June, it will be the largest vessel ploughing the sea.
Each will contain as much steel as eight Eiffel Towers and have a capacity equivalent to 18,000 20-foot containers (TEU).
If those containers were placed in Times Square in New York, they would rise above billboards, streetlights and some buildings.
Or, to put it another way, they would fill more than 30 trains, each a mile long and stacked two containers high. Inside those containers, you could fit 36,000 cars or 863 million tins of baked beans.
The Triple E will not be the largest ship ever built. That accolade goes to an "ultra-large crude carrier" (ULCC) built in the 1970s, but all supertankers more than 400m (440 yards) long were scrapped years ago, some after less than a decade of service. Only a couple of shorter ULCCs are still in use. But giant container ships are still being built in large numbers - and they are still growing.
It's 25 years since the biggest became too wide for the Panama Canal. These first "post-Panamax" ships, carrying 4,300 TEU, had roughly quarter of the capacity of the current record holder - the 16,020 TEU Marco Polo, launched in November by CMA CGM.
In the shipping industry there is already talk of a class of ship that would run aground in the Suez canal, but would just pass through another bottleneck of international trade - the Strait of Malacca, between Malaysia and Indonesia. The "Malaccamax" would carry 30,000 containers.
The current crop of ultra-large container vessels can navigate the Suez - just - but they are only able to dock at a handful of the world's ports. No American harbour is equipped to handle them.
The sole purpose of the soon-to-be-launched Triple E ships will be to run what's called a pendulum service for Maersk - the largest shipping company in the world - between Asia and Europe.
They arrive in Europe full, and when they leave a significant proportion of containers carry nothing but air. (At any given moment about 20% of all containers on the world's seas are empty.)
"Ships have been getting bigger for many years," says Paul Davey from Hutchison Ports, which operates Felixstowe in the UK, one of the likely ports of call of the Triple E.
"The challenge for ports is to invest ahead of the shipping capacity coming on-stream, and to try and be one step ahead of the game."
Overcapacity in the world's ports means there is huge competition for business. Operators cannot afford to get left behind, says Marc Levinson, author of The Box - How the Shipping Container Made the World Smaller and the World Economy Bigger.
"The ports are placed in a difficult competitive position here because the carriers are basically saying to them, 'If you don't expand - if you don't build new wharves and deepen the harbours and get high speed cranes, we'll take our business someplace else.'"
These big beasts of the sea present ports with other challenges too.
Ship owners also want vessels to be unloaded and loaded within 24 hours, which has various knock-on effects. More space is needed to store the containers in the harbour, and onward connections by road, rail and ship need to be strengthened to cope with the huge surge in traffic.
Felixstowe, which handles 42% of the UK's container trade, has 58 train movements a day, but plans to double that after it opens a third rail terminal later this year.
Bigger vessels also behave differently in the water. The wash created by a large ship can be enough to cause other ships moored in a harbour to break free - just as the passenger liner SS City of New York did in 1912 when the Titanic set out on her maiden voyage.
"These days with the increase in traffic, we experience this more and more often," says Marco Pluijm, a port engineer working for Bechtel. "A simple thing you can do is just slow ships down and add some tug boats for better manoeuvring - but that all has cost implications."
There are currently 163 ships on the world's seas with a capacity over 10,000 TEU - but 120 more are on order, including Maersk's fleet of 20 Triple Es.
Bearing in mind that the carbon footprint of international shipping is roughly equivalent to that of aviation - some 2.7% of the world's man-made CO2 emissions in the year 2000, according to the International Maritime Organization - the prospect of these leviathans carving up the oceans in ever greater numbers is likely to be a source of concern for green consumers.
Maersk, however, argues that the Triple E is the most environmentally friendly container ship yet. (The three Es in the name stand for economy of scale, energy efficiency and environmentally improved.)
Source: BBC