No matter where on the water, in an emergency, contact the U.S. Coast Guard by VHF radio channel 16 (156.8 MHz) or by dialing 911 if within cell phone range.
Other Useful Phone Numbers
USCG Seventh District Command Center for emergency: (305) 415-6800
USCG Sector Charleston for emergency: (843) 724-7600
USCG Sector Jacksonville for emergency: (904) 714-7558