In this paper, the authors present an intelligent lure which can avoids rooting by applying a disturbance observer (DOB). This environment-friendly lure has a propeller motor for backward motion. We make a better use of this motor to classify the lure's motions into sinking, being drawing, and hitting something according to a time-series of DOB estimates. Its prototype has been implemented and its ground experiments have been conducted. Experimental results prove we have extrapolated the lure's motions successfully.