Simplify the following text for a Grade 10 native English-speaking person.
Original: So , in 1835 , as a leading member of the Port Phillip Association he sailed for the mainland of Australia in the schooner Rebecca and explored much of Port Phillip Bay .
Simplified: So , in 1835 , as a leading member of the Port Phillip Association he sailed for the mainland in the schooner Rebecca and explored much of Port Phillip .