This Small Business Innovation Research (SBIR) Phase I project will fill a critical need for accurate location and depth measurement of undersea fiberoptic cables. This program will builds on prior expertise in ultra-sensitive magnetic susceptibility detection in the human body. The susceptometry technique provides the high signal-to-noise ratios, and then ability to suppress the background response of bottom sediments, that are needed for accurate depth measurements. At the same time, this program will require significant high-risk developments to maximize the accuracy of depth determination, localize fiberoptic cables 2 m or more below the sea floor, and adapt the measurement system to the deep ocean environment. This program has strong support from industry leaders. These experts emphasize that no existing cable location system provides adequate depth information, and that accurate cable depths are crucial to avoid damage that can cost millions of dollars per second. With more than 680,000 kilometers of fiberoptic cables in the ocean, and the cable inspection market growing at an estimated 30% per year, this new fiberoptic locator system has excellent commercial potential.