Abstract: Two components of the underwater pressure signal of a raindrop impact are identified. An initial single cycle impulse lasting less than 0.1ms is attributed to an acoustic "water hammer" of the raindrop onto the water surface. The second feature, a "plateau" pressure signal with a time scale over 1 ms, is associated with the nearly incompressible hydrodynamic flow of the drop splash. The radiated sound field from the impacts is dominated by the impulse component and produces a broad spectral peak near 15-20 kHz as previously reported.