Simplify the following text for a Grade 13 native English-speaking person.
Original: It is divided into a number of principal oceanic areas that are delimited by the continents and various oceanographic features : these divisions are the Atlantic Ocean , Arctic Ocean ( sometimes considered a sea of the Atlantic ) , Indian Ocean , Pacific Ocean , and Southern Ocean ( sometimes reckoned instead as just the southern portions of the Atlantic , Indian , and Pacific Oceans ) .
Simplified: These divisions are the Atlantic Ocean , Arctic Ocean ( sometimes considered a sea of the Atlantic ) , Indian Ocean , Pacific Ocean , and Southern Ocean ( some people think it is just the southern portions of the Atlantic , Indian , and Pacific Oceans ) .