Rather than flying, travel by train or bus, or car pool. Trains are by far the most ecological option, while there are considerable differences in emissions from ships. This is why you should choose a ship with the lowest possible emissions and continue your journey by train if you want to reduce the carbon footprint of travel. Overland travel is an experience in itself, and you can make use of the travel time and enjoy travelling in different ways.
If completing the whole journey by train is too awkward, only go by rail one way or part of the journey; this will also have an impact on emissions.
When flying, select a direct flight with no stopovers. Choose a propeller aircraft instead of a jet plane if possible as this option has lower emissions. The weight of your luggage affects the emissions, too.
You can also offset the emissions from your flights.
A virtual exchange is another possibility of participating in an exchange with a smaller footprint.