The scientists studied how rainfall affects groundwater levels in a coastal aquifer in Southern Italy. They found that the aquifer's unique features make the groundwater levels change in a complicated way. To understand this, they used a special computer model that simulates how water moves through the ground. The model showed that the groundwater levels can switch from being free-flowing to trapped. By analyzing real data, they confirmed that their model accurately predicts how the groundwater levels change during rainy periods.