Revealing mistake: You can see the threads moving the submarine underwater. (00:04:55)
Revealing mistake: In one scene, Titanosaurous bites Godzilla's lip and hurls him up in the air. It's quite obvious that there's no actor inside the suit, as it is much too skinny.
Revealing mistake: The submarine is obviously a model. It's too small compared to the waves. (00:03:55)