Researchers developed a way to predict extreme runup on natural beaches using data from field experiments. They found that runup height depends on wave setup and swash, which are influenced by factors like beach slope and wave characteristics. The study showed that setup at the shoreline can be predicted using certain formulas, while swash can be broken down into different frequency bands. On certain types of beaches, the accuracy of runup predictions may vary based on the beach's slope. Overall, the model developed by the researchers had an average error of 38 cm when predicting runup heights.