We had an absolute blast on this trip. It exceeded our expectations.
When we booked, all we knew was that we wanted to go shelling. We researched online and debated between Island Ferry and Shell Shuttle. Shell Shuttle is cheaper, but it's just that - a shuttle. It drops you off at a set point and picks you up 2 or 4 hours later. On Island Ferry, on the other hand, the captain asks you what your priorities are and tailors your trip accordingly.
We were lucky that another group canceled on our day so we basically had a private tour! We got to see a tiny island with Pelicans and Herons in trees, a dolphin mom with her calf, and then we went shelling in a totally empty part of Shell Key for 45 minutes (the boat waited in one spot and we got to explore the beach on our own). Captain John was laid back, professional, and full of all kinds of knowledge (the history of the area, the wildlife, and could answer any question we threw at him).
Highly recommend.