Note the depth and you have established the true working range for that particular bait. Another factor which impacts on how deep your crankbait runs is line diameter. Line diameter affects smaller baits more dramatically than larger ones. On occasion I will deliberately use a heavier line as a form of depth control so I can use a particular bait in shallower water or keep one working just above weed or grass lines. Many anglers mistakenly believe the faster they retrieve a crankbait the deeper it will run.
Truth is, every crankbait has an optimum speed at which it performs best.
You need to experiment with different retrieves to find the one which achieves the greatest depth without negating the baits motion and performance. The surest way to achieve maximum depth is to make long casts and keep your rod tip low during the retrieve. Short casts and a high rod tip tend to pull the bait upward long before it can reach its potential depth. My next crankbait consideration is whether to use plastic or wood. I base my decision on several conditions the most important of which is water temperature.