Fishfindershavealreadybeenwidelyavailableinthefishingmarketforanumberofyears.However,thesizesofthesefishfindersaretoobigandtheirpricesareexpensivetosuitfortheresearchofroboticfishormini-submarine.Thegoalofthisresearchistoproposealow-costfishdetectorandclassifierwhichsuitsforunderwaterrobotorsubmarineasaproximitysensor.Withsomepre-conditioninhardwareandalgorithms,theexperimentalresultsshowthattheproposeddesignhasgoodper-formance,withadetectionrateof100%andaclassificationrateof94%.Boththeexistingtypeoffishandthegroupbehaviorcanberevealedbystatisticalinterpretationssuchashoveringpassionandsparseswimmingmode.