Sonar works by sending pulses of sound waves out into the water and recording the waves that bounce back to create an image. A new type of imaging technique, one that works in a similar way to an MRI scanner at a hospital. This advanced technology is finally becoming affordable enough to put into portable devices. The advancement of the sonar technology has been driven by the fishing industry. Good sonar images let anglers know where to find big fish but its the level of sophistication that is making it attractive to law enforcement agencies and search and rescue.

Down imaging sonar uses high frequency, thin sonar waves to produce an incredibly detailed picture of what is beneath your vessel. The high frequency waves are what enable you to have a snapshot of what is beneath you in unreal detail. Side imaging sonar operates in a similar manner, except out to the side of your vessel. Some units give you the option of using several different beams of different frequencies that go out farther than the last beam from your vessel, giving you the maximum range and a veritable sonar net around your vessel. It's worth noting that these sonar types come under a variety of names: DownVU, SideScan, SI DV, etc.