Massive, football field-sized floating islands chocked full of supplies, with few if any ways for the Undead to enter, a Container Ship would seem to be perfect.  With thick steel doors, medical and food supplies plus the actual cargo, these massive ships would seem to be the perfect hideout- far from refugees and infected, self-sustaining for months, and massive.  They have many of the same problems as Oil Rigs, but are even more at the mercy of the larger waves.

Large container ships or aircraft carriers can stay at dock and just have all entrances sealed off. They are strong, less likely to get hit by waves, and retain safety without having to be stuck in the middle of the ocean.

The most important factor, like any Base, is having the right amount of survivors with you. That can maintain the ship and keep it well defended.

EvacuationEdit

Large ships can have many lifeboats, just in case the ship becomes overrun and a quick getaway is needed. Aside from that, aircraft carriers are designed, as the name suggests, to carry aircraft, which can function as transport.