Complex sentence: Moulting Lagoon is a coastal lagoon, or largely enclosed estuary, formed at the mouth of the Swan River and is adjacent to the Apsley Marshes which store and filter floodwater from the Apsley River for gradual release into the lagoon.
Split into simpler sentences: Moulting Lagoon is a coastal lagoon, or largely enclosed estuary, formed at the mouths of the Swan and Apsley Rivers. It is adjacent to the Apsley Marshes which store and filter floodwater from the Apsley River for gradual release into the lagoon.