IT IS NOT THAT YOU CAN NOT CATCH THEM WITHOUT THESE UNITS,HOWEVER IF YOU WANT TO CATCH FISH IN A NEW AREA THAT ONE IS NOT USE TO THAN IT WILL SPEED UP YOUR CATCHING RATIO MUCH,THEY ARE A GREAT SEARCHING TOOL BUT THE BIGGEST PROBLEM WITH THESE UNITS IS THE PEOPLE WHO OWN THEM,MOST DO NOT KNOW HOW TO READ WHAT THE UNIT IS TELLING THEM SO RATHER THAN LEARNING THEM THEY JUST BOAST THAT THEY GOT ONE,HAVE FRIENDS THAT GOT THEM BUT HAVE NO CLUE AS TO WHAT THE UNIT IS TELLING THEM.YES THEY INPROVE MY FISHING MUCH,AFTER FINDING BP WITH THEM I CAN TELL IF FISH ARE IN BP AND IF THEY ARE BIG ENOUGH TO EVEN STOP TO FISH AND I DO THE SAME WHEN I GO BY A DOCK,LOOK HOW MUCH TIME THAT HAS SAVE BY NOT HAVING TO STOP AND SEARCH SPOT,ALSO IF NOT BITTING AND KNOW THEY ARE THERE THEN YOU DON'T MIND TRYING A WAY TO CATCH THEM