europe - australia by ship

well, you need food, air con, washing machines etc. all day, even when you are at home and not on a ship.

So, adding to #36 & 37.
Specs for a 747-400 give us a fuel payload of approx. 215000 US Litres. We can travell roughly 13000km on this, so from London to Brisbane would use up approx 280000 US Litres of fuel. 400 passengers on board would amount to 700 US Litres of fuel burnt per passenger. If we are comparing this to a cruise ship as per post #36, then 4 days sailing is roughly comparable to 2 return trips to London, or 96 hours of flying time (4 days). So we have 2800 US Litres of fuel per passenger, for 4 days of travel.

A cruise ship of similar size (1200 persons capacity) would use god knows how much. Ive searched and searched but have been unable to find any data.

Queen Mary 2 - 19.7 mpg per passenger source (12 tonnes of fuel an hour at 25 knots with 2620 passengers)
Concorde - 17 mpg per passenger source
747 - 100 mpg per passenger source

i was not talking about taking the queen mary 2, but an ordinary container ship

The whole point pudding is that both the plane and the ship are going to travel whether you are on them or not. You are not saving any CO2 by taking the ship and if anything by creating a demand for long haul sea borne travel you are actually supporting an unsustainable industry. The more people that have a mistaken belief that travelling by sea is greener than by plane the more demand there will be for liners like the QM2.

I suspect that, although QM 2 is capable of 25 knots, she does not cruise at this speed but at a significantly more economical cruising speed.

Actually the QM2 has a top speed of nearly 30 knots, to maintain that she uses 2 gas turbine engines on top of the four diesels. These two engines use as much fuel per hour as the four diesels. I didn't include these engines as they aren't used routinely but only as neccessery to get underway or in heavy seas.

Yes the QM2 could save more fuel by running slower however she is a liner, that is she runs regularly scheduled services between Southampton and New York and that is the speed she travels at on this service (published speed is 24-26 knots). IF you want to compare apples with apples then this is long haul sea borne passenger transport.

Well bugger me. I thought that the Blue Ribband days were over and the shipowners were now concentrating on cruising and economical steaming.

Mostly they are. It's only Cunard that maintains a liner which was the QE2 until the QM2 took over the run a couple of years ago. The QE2 now concentrates on cruises.

Ah kurgan. Do you, like me, lament the passing of steam? A quartet of diesel thumpers and a couple of aero engines! Egad! Nature turned upside down!
Then again I suppose 100 years ago people were saying the same thing about the demise of sail. What's worse, I agree with them too.