Electronics have spoiled us and also made us better, but we used to catch fish before. Having the Navionics on your phone is a little help providing you can see the depths ( Im getting old and cant see em without glasses) . If you know whether your dealing with a shallow water weed oriented bite or a deeper water basin oriented bite would also help. The shallow bite is preferred without electronics because the basin bite usually involves fish that may be suspended 2 to 8 or more .feet off the bottom. In shallower water you will be able to cover the bottom 2 feet where 90% of the fish will be ( just remember fish are usually looking in front and above ). Drill a lot of holes and dont spend more than 4 or 5 mins in any one without a bite. Once you get a pattern look at your Navionics and find similar depths, especially if there are fingers, horseshoes, or similar variations in the contour lines. If you must fish a deeper basin bite, look for where other people have been fishing to start with. Go to bottom and
work your way up to 4 or 5 feet off till you get a depth figured out. When you do, you can go to your Navionics and look for similar depths. Again drill lots of holes and move often. Good Luck