geez, you live in Ft. Lauderdale, i can think of lots of ideas!
many creatures and fish are territorial... if you could dive the same spot at least a few times per week you could document a specific creatures life cycle. I like finding a nest of sargeant majors with eggs and taking pictures as the eggs develop and then hatch (I think I was told the cycle is about 10 days but not sure). Also, jawfish hatch eggs in the male fishes mouth, lots of people find them in their hole and go back each day to see how long it take for them to hatch.
another thought is to go to one of the smaller shallow wrecks there in your area and document what critters live on each side - north, south, east, and west, in current or out of current and see if there are differences. Or take a specific fish (like secretary blenny) and count how many are in a 3' radius on the wreck (they live in colonies, building little hole condos).
Or take 4 pvc pipes and make a square, 3' or 4' would be plenty big. Put the square down on the reef and count every fish or critter you find inside the square (take pictures or video, too). This is one of the ways scientists study reefs to see if they are healthy or not.
geez, lots of ideas........ need any more?
robin