FISHFINDER word has been a deceptive marketing tool in years, you can normally spot accurate fish readings only when you are more than 20 feet deep, since the beam diameter opening from the transducer gets wider by then. But if someone was just fishing 6 foot depth, the unit can be misleading, with the clarity of the water these days, just use your eye site to see what is underneath your boat. Most unit also create false fish reading, debries or change in water temp can fool the fish finder to assume it was a fish.
The unit should be marketed as a depth finder. Once you can spot the proper depth, dropped off, baitfish, underneath structure, and right weedbed, the fish will be there. The unit is also helpful to tell a boater surface temp reading and shallow waters are up ahead .
Here is an interesting read http://www.fishdepthfinder.com/behind-every-successful-fish-finder-is-a-good-transducer/
Beam calculator http://www.furunousa.com/LearningCenter/Transducer-Beam-Angle-Calculator.aspx
Understanding fish habitat will help your catching success rate. If you are aiming for bass. They normally hates direct sunlight, they are also predator and likes to hide on some structure or weedbed, but easy enough for them to dart out of their coverings and attack their prey. Except during spring time when they are spawning, they can be spotted on some open shallower waters since the water gets warmer. Otherwise during warmer weather they would rather hide and come out during early mornings, late afternoon and evenings. Change of weather pattern also affects their activeness. The shallower the water, the more vulnerable to barometric pressure change, one main reason fish also prefer to hide on deeper water during inconsistant weather pattern.
http://www.squidoo.com/basshabitat river fishing is good due to rich in oxygen and consistant water temp.
http://www.bassresource.com/fishing/fishing_tips_summer.html deepwater fishing during summer
http://www.bassresource.com/fishing/summer_bass_fishing_tips.html tough summer fishing for bass
