That's 24,5 on average per year, worldwide.
In 2012 33.500 people were killed in traffic accidents in the USA only. Yes, that is just under 100 a day!
Still people worry about their safety onboard a very well maintained and very safe Cruise-ship, while they drive their cars into traffic or even cross the busy street as a pedestrian without a blink.
For
DCL specific, two MOB cases are known. A DCL CM went overboard and is assumed to have committed suicide, she was never found, very sad.
The second was a boy who jumped overboard while the Ship was docked, climbed up again and was confined to quarters by the Captain for the remainder of the cruise.
But to answer OP's question: if you are spotted while going overboard (just falling really isn't possible) you are in luck as the crew will immediately start the MOB procedure and will try to rescue you with a lifeboat.
If you are not spotted you will probably never be found again in the Big Blue. There is no way you can rescue yourself swimming halfway Florida and the Bahama's, simply because you have no way to navigate which way to swim either by day or by night. In the night you will not be visible in the dark Ocean and with a Ship at cruising speed you are quickly left behind.