Crank baits emulate either crawdads or baitfish, depending on the lure you choose. As a general rule, a smaller bill means your bait will run in the top two to four feet of the water column, thus, emulating baitfish. Longer-billed cranks can run as deep as 22 feet when thrown on eight-to-10-lb. line and are designed to bump off rocks much like a foraging crawdad.
The one thing that I know for certain is crank baits catch bass, striped, largemouth, and smallmouth with great regularity.
To get you started during summer, purchase a couple crawdad patterned (red and black) six-to-10-foot divers and go to work on any rock wall in the current or point where you have moderate current flow running in or out of a shallow grass flat. For your diving cranks, your reds and whites are excellent starting points. Fish these on 10-to-12-lb. test and run them as close to the bank as you possibly can.
So you don't get hung up in the rocks too often, reel down until you feel your bait bouncing off the bottom, then use your rod tip and slowly sweep it up current before reeling in the slack. Repeat this process until your bait is back to the boat and start all over again. The other way to fish these is to simply cast and wind. I'll let you in on two things the fish taught me over the years: my biggest crank baitfish were all the result of the sweep method, and cast-and-retrieve will catch bigger numbers. My only explanation for why this is true is that the sweep method keeps the bait in the strike zone much longer, and bigger fish are typically sluggish, so they react better to a slower retrieve.
For a rod, find a six-to-seven-foot bait caster with a soft tip so you don't pull the small crank bait hooks out of the fish's mouth. Find a conventional reel and spool it up with 10-to-12-lb. monofilament line to round out your arsenal.
Overall, there are better baits to catch bigger fish during the summer, and there are more difficult techniques that produce good catches. However, if you are new to bass fishing and the Delta, you will learn and catch more in one day with cranking than any other offering. And, friends, this is no fish story.