Power of monitor part of depth finder is 4XAAA batteries, and sonar transducer use CR2032 coin cell battery (included) as power. At power saving mode, 4 new AAA batteries can provide sufficient power for fish finder to work continuously all day. The wireless handheld fish finder can be used on shore fishing, lake fishing, kayak fishing, boat fishing... both in freshwater fishing and saltwater fishing. Easy to use: Compare the ordinary portable fish finder with wired sonar transducer, the wireless type fishing finder is more easy to use. All you need to do is tie sonar sensor to a fishing line and throw it to water, fishing information will be shown on display. And if you tie sonar sensor to a RC boat, you can easily get the information of fishing point which you just want to detect. High performance wireless sonar sensor: The max wireless operating distance of castable fish finder is 393 ft (120m), and the water depth detect range is 2.3 ft (0.7m)~130 ft (40m) with 90° sonar beam angle. And the operating temperature is 14°F to 122°F(-10°C-50°C) which means the wireless fish finder also can work well on ice fishing in winter. Wireless castable fish finder · depth finder will help anglers get useful fishing information such as water depth, fish location, bottom contour easily and quickly. No matter you are a beginner of fishing or an experienced angler, this castable wireless fish finder will give you a brand new experience of fishing, and if you want to choice a fishing gifts for your friends, husband, father, the handheld fish finder is the ideal one!. Useful functions: Fish & fish school alarm function will sounding alarm when fish are detected which make you no more missing fish. Back light function can help you confirm information on display under sunlight and dark environments. The sensitivity of handheld wireless depth finder is 5 levels select-able, so no matter the water is clean or turbid, the portable fish finder can provide fishing information correctly.