Introductory divers expect little to see while making bubbles underwater. Especially the first time divers have only an abstract idea about fish and coral. In general, there are at least three options for entertaining introductory divers.
The first option is sea cucumbers. Sea cucumbers are often scattered on the seabed in a massive number, but somehow, introductory divers are attracted by these ordinary creatures. An instructor can easily picks up a sea cucumber for customers to hold on hands or even wear the sea cucumber on head. However, it could be controversial for a dive professional to tease marine life.
The second option is giant clams. Giant clams are so large that they can be recognized from a distance. In addition, giant claims stay in a fix location. As long as an instructor is not too bad at navigation, it is easy to find a giant clam and take a photo of customers with their faces right above the giant clam. So, it is often the best choice for photos.
There are more entertainment options in an introductory dive. But, the above options are the most common ones when customers are not lucky enough to encounter a reef shark or a sea turtle.