I would say boredom on expedition in the ocean or on ice is never an issue because there is plenty of work to be done. Field work, as we call it, demands lots of energy, people work shifts and that is very tiring, usually there is not much time to rest. Sometimes there is so called cruising time, when the boat spends few days reaching working location. Even then people keep busy with organizing labs, looking at some data, fixing technical issues etc. There could also be meetings organized, scientists show presentations, discussing different questions and hypothesis.
Even if you get some free time on the boat, there are usually DVDs available to watch, gym, books etc. to keep you entertained.
Isolation is another thing, which experienced scientists don't see as a problem. Modern technology allow us to have access to an email, which helps to keep contact with the rest of the world. There are other people on an expedition with you, at some point you can get tired of seeing same people for weeks, but you know this is not forever and in fact expeditions last relatively short time.