With the proper knowledge and crew, a modern nuclear submarine could be a good base. Having power supplies for years and being able to dodge storms by going underwater, submarines are the ultimate mobile base. Food might be a problem, but some simple fishing gear might very well be used when at surface. However if an accident or breakdown happens, it can be catastrophic. If something breaks at critical places, the base should be evacuated, although this is most likely impossible. Before even thinking of packing up your gear into one of these steel tubes, contemplate long and hard about the dangers of a sub-surface ocean voyage.