Our purpose is to improve the performance sensitivity of a fiber sensor used as a fiber optic hydrophone probe (FOHP) by the addition of nanoscale thin film gold coating. The fiber is designed to provide a uniform and spatial averaging free response up to $100\mathrm{MHz}$ by etching down to an active diameter of approximately $9\mathrm{\mu m}$ . The performance sensitivity of straight cleaved (i.e., full size core and cladding) uncoated, tapered uncoated, and tapered thin film gold-coated fiber sensors was compared in the frequency range from 1.5 to $20\mathrm{MHz}$ in the presence of acoustic amplitude pressure levels as high as $6\mathrm{MPa}$ . An unprecedented voltage sensitivity of $-245\mathrm{dB}$ relative to $1\mathrm{V}/\mu \mathrm{Pa}$ ( $560\mathrm{mV}/\mathrm{MPa}$ ) was measured for a thin film gold-coated FOHP by optimizing the gold coating thickness.