FYI, a 3oz weight at approx. 1.7-2 mph will travel at 2/3 of the amount of line out on a line counter reel, and with a 3' leader, the bait will go down 1' below the weight. ANY diving bait, no matter the size.

To fish a bait 15' deep--
Let out 21' of line = 14'
Bait depth. +1'
Equals. 15'