During the warmer months, you can go snorkelling near the shipwreck for some great sights and sealife. However, you will need to bring your own snorkelling gear (just remember to visit KMart, Big W, or Target to get some cheap snorkelling equipment).
There are toilet facilities nearby at the Lifesaving Club house for changing. Also. the Cerberus Beach House (https://goo.gl/maps/BDKoNasASyS2) is famous for its fish & chips and is great for a meal after a swim.
Beach Rd,
Black Rock
VIC 3193
https://goo.gl/maps/eF1nFZuAUdE2