USF has released the revised Water Atlas's for Central Florida. Hillsborough, Polk, Orange, Seminole, Lake and others. Here is the link.
http://beta.polk.wateratlas.usf.edu/default.aspx
There is a lot of good information about small lakes and even contour maps for most of them.
This link will lead you to the Polk County Atlas. To change counties,
use the pull down tab in the upper right corner to select the atlas. Use the menu in the upper right to select your body of water. Then in the upper middle there is a "Water Level and Flow" tab that will lead you to contour maps.