The reduction of signal‐to‐noise ratio due to hydrophone and preamplifier noise is a critical problem in the design of acoustic receiving systems. A signal‐to‐noise degradation factor is defined which depends upon figure of merit of the hydrophone, the amplifier noise figure, and the ambient noise spectrum. For piezoelectric hydrophones, the figure of merit is determined by fundamental material parameters and the volume of active material. Both voltage and charge amplifier configurations are considered. The charge amplifier is found to be inherently noisier.