I used to be a diving instructor in my late teens to early 20's. (YMCA Instructor) Tac is right on the money. Very boring and can be dangerous. Especially when you have people who thing a dive flag is a marker for doing power slides on a jet ski. From my experience, lake dives can be interesting. Myself and several other volunteers assisted with some research on the red bellied turtle. These were ice dives in Worcester, Massachusetts ponds.
http://www.jstor.org/pss/1565004If you are not sure of yourself, you can tie a safety line to your gear. BUT, I would recommend that you get acclimated in shallow water before doing this. Your safety line can be a hazard if you don't pay attention to what your doing. Safety line training was an additional class we used to teach. The most reliable safety precaution is a dive buddy. In low visibility, don't be afraid to hold hands.
In our classes we used to teach
"Plan your dive and dive your plan." Re-certification isn't required, but there might be refresher courses available.
Good luck and have fun.