When I started diving it was in the Carribean, nice clear warm water, and I felt much the same as you do. I was confident in the water but pretty dicey about being fully responsible for a dive myself. I think this is a natural confidence thing...will I forget something? Can I find my way back? etc. The confidence will come with time, try going through all the motions of leading the dive while following your DM. See if you can track your course with your compass, predict your air consumption and compare your supply with your prediction as you go. Make this a "game" as well as looking at the sights...think of it as practice in the multitasking that is so important to diving.
Also, as suggested by others, do some local diving. There is much more to see than you may think (I'm assuming this is as true in the inland lakes as it is on the coast.). When I took up diving in the waters of Maine and Mass (shore diving with skilled buddies) I found a whole new world. This included a new set of challenges (cold dark water with 20 foot viz on a good day) that I really enjoyed overcoming. In spite of the conditions there is an entire eco system just waiting down there! And conquering the challenges of the northern climes will make you a much better warm water diver. It's well worth seeking out experienced local buddies and diving for experience.
Now when I go to the islands and they make the rounds on the boat to determine everyone's skill level the conversation is like this (DM to the warm water diver)..."where and when did you dive last?" WWD:"uh, last year in Barbados", DM: "How many dives did you do?". "Um three", DM:"ok, stick close by me". Then he turns to me, DM: "Where and when did you dive last?", Me "last week in Maine", DM turns to next diver, "where and when...". It's funny how much skill the other vacation divers lost while I was diving at home, where did all those intimidating "pros" go?
Um, the line about going up like a rocket makes me nervous...you do know that that is anything BUT cool, right? Please review ascent rates and why you should be careful...