The reefs surrounding the islands provide good snorkelling and diving and abound in marine life including sea stars, urchins and molluscs as well as a number of fish species. Take to the water and you'll probably run into a pod of bottlenose dolphins which are extremely common in the marine park. You can swim with dolphins on tours which operate regularly.
Seal Island is home to a colony of rare Australian sea lions which can often be seen fishing and swimming in nearby waters.
Shoalwater Islands Marine Park is also home to the Saxon Ranger, a 400 tonne former fishing vessel - the first purpose sunk dive wreck in the Perth metropolitan area. Dive permits are required.
Shoalwater Islands Marine Park is accessible from Rockingham which is less than an hour's drive south of Perth. Please note that costs may apply for some activities.