What are characteristics of all three modes of transport (land water air)? Which will be most dominant in the future?
I would argue that water transport will be dominant for cargo wherever possible. Land transport will be dominant for cargo in landlocked areas and will be dominant for passenger transport as well across relatively short distances. Air transport will only be dominant for long distance passenger travel and for the transport of cargo that is very valuable relative to its size. All of this is true because of the characteristics of these three modes of transportation.
The three main characteristics of water transport are that it is slow, that it can carry large loads, and that it is relatively cheap. Modern ships can carry huge loads of cargo without using very much fuel per unit of cargo. This makes this type of transport very cheap. However, water transport is also very slow as even modern technology cannot make ships that will go very fast. All of this means that water transport is the cheapest way to move large cargos that do not have to be somewhere in a hurry.
Land transport’s main characteristics are that it is more expensive than water transport (but cheaper than air transport) but also faster and able to reach more places. Land transport will dominate in landlocked areas simply because water transport, while cheaper, cannot reach those places. It will dominate for passenger transport across relatively short distances because it is cheaper than air travel and also because air travel can take up a lot of time when you have to go to an airport hours before your flight and get from the destination airport to your actual destination. By contrast, automobiles allow you to go directly from Point A to Point B at a time of your choosing.
The main characteristics of air transport are that it is fast and expensive. It will dominate for long-distance passenger transport and for the transport of high value cargo because it is so fast. However, it will not dominate for anything else because it is so expensive.