Functions of handheld depth finder: Real-time display water depth, fish location rock and weed.5 levels adjustable sensitivity for clear water and turbid water. Background light for night fishing(on/off). Fish detector alarm(on/off). Save powder mode(on/off). At the save power mode, the handheld depth finder can be used consistently at least 6 hours. Wide detection range: The max detection depth of portable fish finder 818 is 328ft (100m) with 45detecting degree. And sonar transducer frequency is 200Khz. The sensitivity adjustable function make the portable fish finder 818 have an accurate detection anytime, no matter the water is clear or turbid. (Tips: please use a low sensitivity when water is turbid) The operational temperature of portable fish finder 818 is : 14 to 122(-10C to 50C). Fish finder all season Easy to use: The usage of handheld depth finder is very easy. All you need to do is put power on and throw sonar transducer into water. With the mini size, handheld depth finder can be used places like: canoes, kayaks , pontoon boats, jon boats, row boats, ski jets , float tubes, bank, dock. And if you always fishing bass, crappie, trout, use portable fish finder 818 is an absolutely good way to get a good catch