Interaction of two vessels during head-on encounter acts as short and strong force. Consequences can reflect on vessels’ handling causing unwanted effects. This phenomenon was elaborated in the paper, considering influence of interaction force and its dependence on main recognized factors: mutual vessels’ distance, speed and depth under the keel. Besides interaction force components, analyses comprised other relevant factors as vessel’ heading, course alterations and drift of vessel due to interaction. Planned and, according to main factors, defined scenarios were conducted in navigational simulator with usage of navigational areas creation tools. After simulations and data post-processing, obtained results were summarized. Correlation of results with mathematical relations describing interaction was conducted. In the conclusion chapter, final inferences are stated, with some of observations which in the opinion of authors are significant. Conducted analyses, obtained results and derived conclusions represent basis for further research, thus future activities regarding interaction phenomenon are proposed.