I don't think we could ever say with certainty if Titanic broke in two at the surface. Perhaps it happened beneath. One theory I made though not very likely is that the stern section imploding or exploding caused the stern to separate from the bow section. Also I believe that the stern section actually exploded rather then imploded as many believe. The stern of course was not fully filled with water when it sank, so the water and air inside caused massive pressure and I don't think it was at a deep enough depth to be crushed by the pressure of the water, however the pressure building inside was intense and eventually popped and caused the damage we know today. The explosion caused the poop deck to curl back on itself.