Fishers can be divided into a few groups insofar as their opinions on portable fish finders. Some do not know they even exist. Others are aware of them but have never used them.
Most of this group are looking forward to getting to use them and possibly buying one for themselves, but a small segment do not want to ever use them, since they are strict sporting purists, who believe it just is not fair.
For the vast majority of fishing enthusiasts, portable fish finder are an absolute dream that has come true, like x-ray vision to see where the fish are. They are held in the hand and can be used in boats, on piers & bridges, on the shoreline or even on the ice on top of frozen lakes. They not only display the fish, but the weeds or other things that could be a problem, and they provide data on the actual depth.
They way they work is with SONAR, which stands for sound navigation and ranging. Dolphins and bats have it, naturally. These devices, emit a signal that is an electronic sound that goes into the water and bounces back, with the information.
The fishers that call the use of fish finders a form of cheating, take the position that Fishing is not just about the act of getting the fish. It is about the entire process that goes into it, and that using technology to find the fish for them, would take away a lot of the feeling of satisfaction that they get from fishing.
It is a matter of personal choice. Few people would consider it a moral issue. Another example would be hunting. Some hunters may use a dog while others choose not to. The only way there is a genuine ethical issue if is there is a competition and the rules do not allow outside help. Beyond that, most people who enjoy fishing would consider the real sin is to have this type of tech available, and to deny yourself from ever experiencing it.
Portable fish finders can cost more than a thousand dollars but less than 1 hundred dollars. The more expensive ones are good for up to 100 foot depths and they have larger screen displays, in color, with superior resolution. They provide more data for wider areas. The less expensive models are better for fishing in shallow water. The screens can be hard to read in direct, overhead sunlight.