There are numerous problems, however, and the aforementioned fires are only the tip of the iceberg (icebergs may also be one of the problems, especially in polar regions). Hurricanes are probably the largest threat, but pirates are yet another problem, so remember to keep weapons and plenty of ammunition, and if you brought large, impractical-against-zombie weapons like a minigun, it's best to leave it out where potential thieves can see it and rethink their options. Corrosion of your equipment is another major worry, and as little else rusts metal faster than a sea breeze. Mother Nature will be your biggest enemy, from stormy seas, to brutal icey winters intensifed by the ocean air (where applicable).
The Offshore Oil Rig is a unique holdout point, though rarely is it accessible enough to be an option. It can be a terrific short term bastion, but for long term survival, supplies will need to come from the mainland. Maintenance of both the facility and the sea vessels may be difficult, but crucial for survival.