That sounds like a dicey business for sure. Depending on the vessel it can take some time and effort to fire up the engines and get underway, especially if it's been sitting for a while. Not to mention all the stuff that can go wrong, like casting off a stern line and getting it wrapped around the prop. That's working for a living!
On an unrelated note, I've always thought that building an offshore city would be a hell of a cool thing to do, and a neat way to create your own country.
Does anyone know good resources for geeking out on things maritime?