Revealing mistake: While tossing a baseball with his son, Ray calls him a "dick." If you look at his hand at that point, one can notice that his hand is closed in a fist, and he is not holding the baseball he is prepared to throw. (00:10:10)
Revealing mistake: Dakota Fanning cannot actually see the computer generated birds that are flying high over the Hudson-Athens ferry. If you look closely her eyes stair straight ahead and not up in the air where they should be. (00:58:35)
Revealing mistake: When the Hudson Ferry captain casts off the large label that reads "Hudson Ferry" is on his left side of his jacket. However, in the exterior shot as he looks out the window at the whirlpool, the label is on his right side. This shot was flipped, and amusingly, the CGI guys actually retouched the words "Hudson Ferry" so it wouldn't read backwards. (01:02:25)
Revealing mistake: At one point when Cruise is driving through the county in the van, you can see that the van is actually in "Park." You can notice this because the column mounted transmission lever is all the way up.
Revealing mistake: When the tripod is tipping the ferry over, people fall over the rail and cars slide toward it. You can see the cars stop short of the rail so they don't smash into stuntmen, even though they are jammed against the rail in the next shot.
Revealing mistake: After the ferry scene, CGI clothes fall off from the sky, but manage to go through the branches of the trees, without becoming entangled in them, or without the branches affecting the falling path of the fabric.
Answer: They're reported to be about 100 feet tall.
Which is about 30.5 meters.
lionhead
They definitely seemed a lot taller than 100ft in the movies though that's for sure. I would have guessed maybe a few hundred feet.