Georgia aquarium was a very good one timer (two for me)
On top of a free tee shirt, you also get a very nice grocery bag. (making a little joke here, but they do give you a nice bag.)
I did it with my brother and then with my wife and daughter. It is very well put together - you get to see them shoveling whatever it is whale sharks eat behind small boats and they munch it down.
Mantas also play in your bubbles and there was my personal favorite a saw toothed shark.
The briefing is good and you do see some really cool stuff. (its quite cool how thick the glass is and on my second dive, even though she was warned, my instabuddy rocked her face right into it)
As earlier noted, I was annoyed I had to pay to get in to have the privilege of spending 300+ on a dive. The first time it was included.
That being said, this is a biblically good dive for a parent and a younger newer diver. Something they won't forget, and they don't care about it being 30 minutes etc, they will just jabber on about how cool it was to almost get trucked by a whale shark.
I am with Kharon, the video they sell you stinks, but...with my daughter there, had to get it.