A depth finder is a piece of sonar equipment designed to be portable. They are frequently used by fishermen who catch fish from a boat and want to know both the underwater landscape of the pond or lake they are fishing in, what kind of conditions exist under there and if there are any fish around. Without spending a lot of money, you can use a depth finder to give you this and more basic information about what is under your boat.
A depth finder uses sound waves to bounce off the bottom of the body of water and any obstruction that are in the way. A lake with a solid bottom will show a strong line on the depth finder. One with lots of muck or clumped vegetation will show a wavery, soft line instead.
Some depth finder apparatus actually show if there are fish below you and may even have symbols that show up to supposedly show exactly where each fish is. Unless you have a state of the art depth finder with precision measurement and nothing is moving at the time, you will get approximations more than exact readings. Still, the information given by the finder can greatly increase the chances that you find fish to catch and are able to catch them with your gear.
A depth finder is a great piece of outdoor sporting technology to add to your arsenal of fishing equipment. It can help you turn even the best day fishing into a much more successful one.