Underwater radiated noise from marine vessels is a growing problem, with a large body of evidence now showing the detrimental impact this is having on marine life. Whilst most of the discussion currently focusses on the impact of large vessels, recent evidence shows that small vessels can dominate the soundscape in shallow coastal waters. In this study, acoustic trials are carried out on two small vessels: a pilot boat and a rigid inflatable boat (RIB) across a wide speed range. The average source levels range from 156–173 dB for the pilot boat and 164–166 dB for the RIB (re1μPam). The engine noise is dominant for the RIB across the speed range, and it is further shown that the heading relative to the prevailing waves is a bigger determining factor for noise levels than speed. In upper sea state 3, the overall sound level is up to 6 dB higher when in head waves compared to following waves. Acoustic measurements are combined with onboard vibration measurements to provide further insights into the relationship between noise and vibration. Analysis of this data shows the vessel running attitude plays a key role in determining how much noise is transmitted into the water.