Listen to these actual off the air recordings of two SOS signals on 500 KC from a few years ago.  The first part is a relay from shore station GLD who heard the "Mayday" from the Henriettab on the international voice frequency of 2182 kHz and relayed it to ships who monitored the cw frequency.  The Henriettab had 13 lives on board.  The second is the passenger ship Prinsendam, who had 510 on board.  That’s a total of 523 lives at stake in just these two instances.  The Prinsendam recording starts with the last two bars of the auto alarm (two 4 second dashes separated by 1 second).  The auto alarm is actually 12 four second dashes separated by 1 second to draw attention to those listening that a SOS is going to follow.  Notice the sending stations were sending with the best “fist” they could.  Definitely not trying to snow anyone with their fancy fist or speed of sending, they wanted everyone to get 100 percent correct copy.   That is the name of the game on cw, accuracy, not speed.  CW gets through when nothing else will.  CW can be sent with a light, horn, mirror or even smoke signals.  SOS has even been scratched in the ground, in snow and even set up by arranging rocks on the ground to be seen by a rescue plane.
     Almost everyone knows SOS, but if you need to say something else, like “need medical” or “food” then you need to know the code.  Learn CW!  Notice how skilled these maritime cw operators are.  Imagine sending an SOS with a ship listing 40 degrees in rough seas.  As a CW op that has had the experience of having to wear a seat belt and sending a message while being tossed about in 40 foot seas I guess the closest feeling I can think of would be to try texting a message to someone while riding a roller coaster.

Why we learn cw!
Prinsendam SOS
Henriettab SOS