I've done a few "specialty" dives, including the Stuarts Cove Shark Dive.
When my then high school aged son and I did it about 5 years ago it consisted of two dives at the same location. The first was a generic guided dive at about ~30 fsw where you may catch a glimpse of reef sharks swimming by. The most interesting part of that one for us was I did find two shark teeth on the sandy bottom - which was something they mentioned to look out for during the pre-dive briefing.
For the second dive, they place you individually next to pre-positioned rocks in a large circle whereby a guide in full chain mail attracts and feeds the sharks using a metal pole with fish he extracts from a metal box. After doing this a number of times from the center of the circle, he moved in rotation to the front of each diver so you can get an even closer view of the strike as well as photo opportunity by the staff photographer as it happens.
The photo of my son with the teeth baring shark made it into his senior high school yearbook when they asked the students to send in "What you did over the summer" photos and the teeth we found on the first dive made a nice keepsake.
We've also done the Manta Ray dive on the Big Island where they similarly place you in position to view the Manta feed on the plankton attracted by pre-placed lights as well as ones held by each diver. Amazing to see how graceful the Mantas are as they move and flip backwards - sometimes two in mirror image synch.
The Pelagic Magic dive on the Big Island is a night time dive where you are tethered to the boat above a 3,000 foot abyss where you have the opportunity to view the different life that you would never see in normal daylight Simply amazing! I wasn't in the water more than a minute before a squid swam directly into my light, and after a second to recover from the unexpected impact, released a cloud of ink - all a single foot in front of me.
In general, at least for most of the ones I have done, these "specialty" type dives aren't your typical swim around and look at things type diving as much as an "experience" that doesn't require much scuba skill than an entry level diver would possess.
At the same time, we've also done a hammerhead dive in Hawaii where there were advanced level requirements as the location they visit generally has strong currents with a drop entry and trailing line exit.
My suggestion would be to speak with the operator to find out more specifics about a particular dive and any skill requirements needed.