Watched it as a kid so really curious. Ok, so there is a weird monster. (I never got to see it clearly though.) This monster keeps killing people. 1.) scene: A special police unit investigates an opened manhole cover during midnight. The head of the team stretches out his head to see what's in there. But then it's chopped of by this creature and other officers back off. 2.) A woman and a child are on a ferry boat. Her child leans against the railings to because he saw something. As soon as he does the creature grabs and takes him into the sea. Bloodbath. 3.) Not sure if it's on the same ferry but a worker goes down to the bilge where he sees something. Suddenly he's attacked and you see his blood all over the place. And ?
no idea sorry
first thing I thought was C.H.U.D. when I read manhole cover, do not recall the details of the movie, or if it fits the other scenes you mention - try googling it or imdb.com