Early in 2020, a client approached us with a problem with aquatic risk assessment that is common to many companies and for many products. “How can we determine the optimum mitigation options, application rates, crop growth stages and application timings for all the separate countries in Europe?” There is a trade-off between all of these factors, and it can be hard to find the best solution, especially because countries have slightly different ways of choosing the options. Each country has its own requirements on which FOCUS scenarios are relevant and which mitigations are acceptable. This means, for example, that one country may allow a wider drift buffer than another and thus a higher rate of application. One country may require any single runoff scenario to pass, whereas another may allow a label restriction based on soils covered by the D2 drainage scenario. Of course, this problem can be solved using the standard tools of SWASH and SWAN: the real question concerns finding the optimum solutions quickly, without endless iteration and revision.