As the Australian Academy of Science points out:

“The fastest trains in commercial operation today are the French ‘train à grande vitesse’ (TGV), the Japanese ‘shinkansen’ (or bullet train) and the German InterCity Express (ICE). The TGV routinely travels at 300 kilometres per hour through the French countryside and has been clocked at 515 kilometres per hour in test runs. The bullet train averages 262 kilometres per hour between stations and has recorded 443 kilometres per hour in test runs, while the ICE has a top operational speed of 280 kilometres per hour and has recorded 408 kilometres per hour in trials.”

In terms of greenhouse-gas emission, according to the UNEP:

“In terms of travel, trains are by far the most climate friendly mode of transport, but how much they actually save depends on how many people are on the train and what energy source it uses.

“For example, trains in Switzerland run on electricity from a mix of hydroelectric and nuclear power. In Norway trains use 95 per cent hydroelectric power. Local shopping malls are also located close to public transport stops. In France, trains run on nuclear power, as most of the country’s electricity is nuclear-based.

“Transporting goods by train is also the most carbon friendly way. Shipping one tonne of goods by train in Europe emits 2.3 kilograms of CO2 equivalent into the atmosphere. However, transporting the same in a short haul plane will emit 330 kilograms of CO2 equivalent, 209 kilograms on a medium hall plane (travelling 5000 – 8000 kilometres) and 117 kilograms on a long haul plane travelling more than 8000 kilometres.”

As the UNEP points out, the source of electricity generation is an important consideration.

Japan’s electricity generation is from a mix of fuel sources. The major sources being nuclear and LPG. Nuclear energy, as you would be aware, may not produce the harmful greenhouse gases, however in my opinion, nuclear waste is unacceptable and should not be considered as an option to fossil fuel generation.

“Today[2006], hydroelectric power, nuclear power, coal and natural gas are used for base load and mid-range load whilst oil is used for peak loads together with pumped storage hydroelectric power.

Of note is the number of nuclear reactors in use.

“The 52 existing nuclear rectors operating in Japan supply one third of the nation’s electricity, giving it the third largest stock of nuclear power plants in the world, after the US and rapidly catching up with France”.

For more information take a look at Sharon Beder’s report http://www.uow.edu.au/arts/sts/sbeder/japan.html

As for sea travel.
“The worldwide fleet of 90,000 ships transports 90 per cent of the world’s goods, and shipping emissions are projected to grow by more than 70 per cent by 2020, as global trade expands.

“In terms of sea travel, an unpublished report by the International Maritime Organization revealed that shipping emitted around 800 million tonnes of CO2 in 2007. This amounts to around three per cent of global emissions. For many years shipping had been thought to be one of the better forms of transport for keeping GHGs down, but studies show that its global CO2 emissions are double those of aviation, and rising rapidly” (UNEP).

For more facts and figures see the following address
http://www.unep.org/climateneutral/Topics/Transport/tabid/154/Default.aspx

Sorry for the long reply, but I hope the above information helps, or at least guides you in the right direction.