Simplify the following text for a Grade 6 native English-speaking person.
Original: Okeechobee covers 730 square miles ( 1,890 kmÂ ) , approximately half the size of the state of Rhode Island , and is exceptionally shallow for a lake of its size , with an average depth of only 9 feet ( 3 m ) .
Simplified: Lake Okeechobee covers about 730 square miles ( about half the size of Rhode Island ) .