Plot hole: The creature gets caught in the fishing net and (after a struggle that shook the whole boat) freed itself. The scientists, upon drawing up the net, find one of the creature's claws, and thus they now seek its source. Shortly after, while Mark is busy loading a harpoon gun, Dave is protesting, stating, "This...this thing *alive* and in it's natural habitat..." It would seem that at this point, they know the creature is *not* dead, but very much alive. They dive, they see it, Mark shoots it with a harpoon, and then upon surfacing, they argue a bit before reporting what they saw to everyone else. So why after seeing it underwater, fully knowing that "this thing (is) alive," do they act so surprised to see it, as if they didn't have a clue it could possibly still exist?