The endangered Kemp's ridley sea turtle was found almost frozen to death off the coast of the Netherlands in 2008, LiveScience.com reported.
Marine biologists say they suspect the animal became trapped in cold currents and was "cold-stunned," an often fatal condition that shuts down internal organs.
Workers the Rotterdam Zoo nursed the animal and then sent it to the Oceanario de Lisboa aquarium in Portugal for further recuperation beginning in summer 2009.
The turtle was flown back across the Atlantic to the Mote Marine Laboratory in Florida, where scientists released it Tuesday into the gulf waters that are the Kemp's ridley sea turtles' normal home.
The animal has been fitted with a satellite transmitter to track its location after its release, they said.