Limestone bluffs are more porous than most anglers realize. Most will have a variety of underwater holes that make great habitat for bass. Last fall, I had a real strong pattern going on Lake Champlain. The bottom looked like a patchwork quilt, and the fish were using the darker spots for camouflage. That was an example of where the bottom composition helped me catch more fish.
Sandy bottoms enhance the growth and variety of aquatic vegetation.
Maidencane, a universal reed-like vegetation, grows on firm soil. Shellbeds can be a gold mine for fishermen. I go in the country. Fritts agrees with Thliveros' assessment of shell-littered bottoms. A few examples of what I look for are sheer rock turning to broken rock, gravel turning to sand and mud turning to clay.