When they send a distress call for help from any near-by ships, they send a CQD morse-code message in the film. However, in reality the CQD
distress call was replaced by the SOS the same year that the Titanic went down. The Titanic was actually the first ship to ever use the SOS, they alternated from SOS and CQD - not just
the CQD used in the film. Also, because the new distress call was only new, the near-by ship didn't recognise it for what it was, and didn't come
to help.