Lure diving depth

A crankbait's bill, the plastic lip on its nose, works like a dive plane. Water pressing on it drives the lure down and gives it its wobble, and the bill's size and angle set how deep the lure runs: bigger and flatter dives deep, smaller and steeper stays shallow. The number on the package, say 8 to 10 feet, is that design depth under typical conditions.

Why depth is the first decision

Fish hold at a depth, usually near something, and a lure swimming five feet over their heads mostly goes unwatched. The productive zone is at or just above the fish, and better still in contact with what they are holding on. A crankbait ticking bottom or deflecting off a rock kicks sideways and breaks its own rhythm, and that stumble is a well-documented strike trigger. So pick the bill so the lure just reaches the structure you are fishing. Too deep for the spot and it plows mud and fouls; too shallow and it swims over the show.

The depth bands

• Squarebill, 0 to 5 ft: short square lip, tight wobble, built to bang through shallow wood and rock and deflect rather than hang.
• Medium diver, 6 to 12 ft: the mid-depth workhorse for points, weed edges, and flats.
• Deep diver, 15 to 25+ ft: long raked bill, wide body, real resistance on the retrieve. Offshore structure territory.
• Lipless: no bill at all. It sinks, so it runs at whatever depth your countdown and retrieve speed give it.

What moves the number

The printed depth assumes a long cast and a typical line. Thinner line pulls less water and lets the lure run deeper, so dropping from 14 lb to 10 lb fluorocarbon can buy a couple of feet. A longer cast gives the lure more runway to reach full depth, and a low rod tip adds a little more; a deep diver on a short cast never gets there at all. Deep divers also pull hard enough that a low gear ratio and a moderate-action rod are the standard pairing: the gearing saves your wrist and the softer blank keeps the trebles in the fish.