Abstract: An elongated resilient cylindrical tube capable of returning to its original shape after being forceably deformed has a closed end and an open end. A sleeve is fixed to the open end of the tube. The tube is filled with buoyancy material and a plurality of different colored dyes, and the sleeve is sealed with a weighted plug coupled to a fish hook. The probe is submerged in the water, and descends due to the weight of the plug. The plug unseals the sleeve when the force of a hooked fish is exerted upon it, causing the probe to ascend toward the surface. As the probe ascends, the different colors of dyes are successively expelled from the probe. The color of the dye which is first expelled by the probe when the probe reaches the surface is indicative of the depth at which the plug was removed from the body.