Here's the info I found on All Ears. I didn't even realize that there was an SAS Adventure. We've only ever done the free portion and thought it was great!
What is Shark Reef like?
Shark Reef is one of the most unusual water park attractions you will ever come across. As you enter the area, CMs behind the counter will hand you a face mask, snorkel and life vest. (No extra charge!) You pass around the reef and along a rock cliff wall. At the entry point, you sit on the ledge and are given instructions on how to use the mask and snorkel. Then its into the chilly salt water to ogle the tropical fish and yes, live sharks. (They're small and harmless.)
Unfortunately, lingering is not encouraged here and you will probably be required to swim straight across the 60-foot pool -- and out. Less hardy souls can view the goings-on from the portholes of an old, upside-down freighter that conveniently sank right in the middle of the pool.
To document your encounter, you may want to consider bringing one of the relatively inexpensive single-use underwater cameras (about $10) that are widely available.
Shark Reef gets crowded quite early, so try to visit first thing when the park opens.
What is the SAS program at Shark Reef?
For those who want to spend a little more time "swimming with the fishes," Shark Reef now offers a longer program called the S.A.S. Adventure. It's a chance to learn Surface Air Snorkeling, involves using a "pony" tank and a small regulator as in SCUBA diving, as well as a buoyancy vest. There is an instructional overview and then you may spend a half-hour snorkeling. The fee is $20 per half-hour for the first person; $15 for the second person. Participants must be at least 5 years old. To sign up for the S.A.S. Adventure, and for more information, visit the kiosk near the entrance of Shark Reef.