Abstract This paper reports on an investigation into the influence of a pre-existing wave environment on ship motion experiments. A method is presented that enables appropriate wave thresholds to be set to ensure consistent, accurate and repeatable results, while minimising waiting time between runs. In addition, the optimal use of a wave dissipation device (or side beach) has been examined to maximise the productivity of the tank by minimising the time between runs. A system has been developed to continuously monitor the water stilling in the towing tank during the time period between runs. The software, written in LabVIEW, provides the towing tank operator with a signal when it is appropriate to commence the next test run. The use of the proposed method and analysis system was examined through a series of monohull head sea tests. It was found that total waiting times between runs may be reduced from the current practice of 10 to 20 minutes to an optimum of approximately 5 minutes without compromising accuracy.