In the scene where Rose and Jack are running from Cal, they run down a set of stairs to the 1st class dining hall. If you look out the windows in the background, it's light outside! I though that the Titanic sunk at night!?
I noticed this too...but then again there were lots of lights on the Titanic, perhaps what we see is the glare from the lights, or they were backlit like the other person said.
In fairness it is possible that the windows were back-lit, but wouldn't there be sparks as the electricity sparked the water like in the scene were Rose rescues Jack from the master at arms' office?