Peter West: What is all this about the dead coming back to life again and... having to be killed a second time? I mean, what the hell's going on here?
Peter West: Out there! They're coming back to life! They're everywhere.
Newspaper Editor-in-Chief: West, keep the British accent out of your prose. Don't take advantage of the fact that your uncle owns the paper.
Peter West: As if I would.
Chosen answer: After the original zombie extra fell ill, the shark handler was made up to play the underwater zombie. The shark was tame, or at least enough to not attack the handler. The makeup would have been latex/oil based, so it would not have been affected by the water. I remember from the commentary that the filming took 1 or 2 days.