Fishfinders & GPS
There's a lot of water out there to cover and electronics help you to shrink it. Most fish activity is out of site below the water's surface. Birds diving on breaking fish is like an iceberg. It's only 10 percent of what's happening. Often the fish are feeding deep and without a fish finder you'll never know.
A GPS provides a lot of useful information. It tells you where you are on the water at all times. You can mark structure that holds fish or where you caught fish. Should fog roll in you'll know where you launched from, etc.