The couple were swimming with a red float, appearing fine one minute and under water the next, witnesses told CNN affiliate WSVN.
Beachgoers along with Ocean Rescue guards rushed to pull them from the water, according to WSVN.
The couple were in cardiac arrest by the time rescuers reached them, said Capt. Adonis Garcia, spokesman for Miami Beach Fire Rescue.
The incident was one of 50 rescues made Sunday due to rip currents, Garcia said, adding that he has never seen a day like it.