I did it about 2 years ago. . .and everything was included in the park ticket, gear and all. Be sure to buy an underwater disposable camera. It will be worth every penny when you see the pictures.
It was great! And I will be doing it again when I go back in October.
I don't think that you will be allowed to bring in your own equipment. They take pretty good care to clean and disinfect the equipment before they had it out.
I hope your not expecting too much from the Shark Reef. It is a pretty quick swim across and you are not allowed to linger (unless there is no one else waiting to start).
Even if they did allow me to bring my own equipment in I don't think that I would because I wouldn't want to keep track of it for the rest of the day.