1、Sonar Sensor: Fish finder sonar sensor can be attached to the hull of a kayak or boat to learn about changes in water depth as you pass by. When the sensor is fully immersed in water, the water depth detection range is between 2ft (0.6m) and 328ft (100m). 2、Data Readings: Portable fish finder shows water depth, approximate fish location, fish size, short tall weeds, sand and rocks on the bottom. Throw the sensor into the water and turn on the display unit, it will show the water depth and approximate fish depth if a school of fish passes by. 3、Portable Design: Kayak boat fishfinder is sized to be held in one hand only. You'll find a lanyard in the package that you can wear around your neck when you're busy kayaking or on a boat. At the same time, with 5 level sensitivity adjustment, you can fish in clear water or muddy water. 4、Fish and Fish Schools Alarm: Once the fish finder sensor is thrown into the water and the display unit is turned on, you will be alerted when fish or schools of fish pass by. It can work continuously for at least 4 to 5 hours with brand new batteries. 5、Ideal Gift : Handheld fishfinder can be easily used in boat fishing, ice fishing, shore fishing, whether in freshwater or saltwater. Portable fish depth finder is a finder gift for your husband, father, friend or any angler.