To me it's all about the ship. If I've made a trip to a port to see a specific ship, or happen to see one when I'm at a port, I might take a risk and climb a fence etc to get a shot, but otherwise I take what I can, when I can, without taking any risks.
I'm lucky that I can enter my local ports as I do occasional volunteering for the local seaman's mission. I take shots when I'm there but only the easy to get vessels. I used to work in the shipping industry, both afloat and ashore, so that gives me a good back catalogue, as I took many photographs then. Nowadays I usually go to riverside or public places where there is no security. Fortunately where I live, and regularly travel to, there are plenty of such options.