What killed the men on the boat?

In The Lost World:Jurassic Park (film), the men on the boat that took the t rex over to San Diego where found dead with no explanation whatsoever. In the original script, instead of the T Rex, it would be Velociraptors, who killed the crew on the boat. We don't see or hear from Velociraptors so either it wasn't them, or there are Velociraptors in San Diego. So what do you think killed the men, tell me about it below.