A modular decision support system developed by Amarcon BV for avoiding dangerous situations in adverse weather and sea conditions. The system combines information from wave measurements, weather forecasts, speed, course, route and the loading conditions to allow continuous monitoring of ship responses, possible hazards and their consequences. Octopus gives a warning, if and when a signal is expected to exceed the critical level, or when there is a risk of ship motion resonance. Clear guidance is given on how to find an operating point in which all the criteria are satisfied by changing the speed and/or course.