Simplify the following text for a Grade 5 native English-speaking person.
Original: St. Catherines Island , also known as Santa Catalina , is one of the Sea Islands or Golden Isles on the coast of the U.S. state of Georgia , 50 miles ( 80 km ) south of Savannah in Liberty County .
Simplified: St. Catherines Island is an island off the coast of the U.S. state of Georgia , 50 miles ( 80 km ) south of Savannah .