Simplify the following text for a Grade 10 native English-speaking person.
Original: Another link existed between Arnhem Land and New Guinea , at times enclosing an enormous freshwater lake ( Lake Carpentaria ) in the center of what is now the Gulf of Carpentaria .
Simplified: Another link existed between Arnhem Land and New Guinea , at times making a big freshwater lake , Lake Carpentaria , in the center of what is now the Gulf of Carpentaria .