You can survive in the middle of the ocean for a short period of time depending on the water temperature.
If the ocean water is 41 F you can survive in the middle of the ocean for around 1 hour and if the ocean water is 50 F you can survive for around 2 hours and if the water is 59 F you can survive around 6 hours and if the water is 68 F you can survive for around 25 hours.
No matter the temperature of the water in the ocean you will eventually succumb to hypothermia when staying in the ocean water for too long after a number of hours.
Your body temperature and core body temperature will gradually lower below the survival temperature.
If you have a cellphone that you can use and it gets a signal and has not gotten wet you should call emergency services such as 911 and report that you're in the middle of the ocean but it can still be hard to determine where you're at.
Always let someone know that you're going to the ocean and when you plan to return and tell them if you don't come back within a certain time to call 911 and tell them you're supposed to be at the ocean so they can hopefully get emergency services to you in time.