This study describes ultrasonic reflection at a water/fiber reinforced polymer composite/water interface. Theoretical predictions of reflected beam amplitudes are also presented. Four different polymer composite laminates are investigated : T300/5208 graphite/epoxy $[0]_{31T},;[45/90/-45/0]_{3S},;[45/-45]_{2S}$, and S-2 glass/epoxy $[0/90]_{4S}$. The analytical leaky plate wave dispersion curves for the unidirectional laminate and other three laminates can be obtained by searching for the minimum magnitude of the reflection coefficient.