Man I wish that all people would wait through the credits of films; what's the rush to evacuate the cinema? I stay through all credits, for the chance that there may be something interesting in or after the credits, or just for a nice piece of music, or to pay respect to the filmmakers.
Anyway, from what I can remember:
The film continues while the credits are being played, repeatedly cutting from video to a black screen with the credits on.
You see all the characters on the boat, filmmed through an amateur camera that you presume the characters find there. They are quick edits, with each shot being about three seconds long. Most shots are just them joking around, you see some nice breasts :-), and then they discover an island. You see them get off the boat at the island, thinking they're safe, then all of a suddent zombies run out from everywhere and kill all of them.
These credits were well done as the editing is quite powerful I think. Anyway, it doesn't really add anything to the overall story of the film, so you haven't missed much.