system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do remote islands have freshwater springs / waterfalls?
gpt
Rain can still recharge the groundwater of an island percolating down and folling in cracks in the rock or porous sand. Typically the freshwater sits atop the denser saltwater, so that if a well drawing groundwater is overpumped it will start to pull in saltwater. This same potential to overdraw freshwater and cause saltwater intrusion happens in coastal areas of large continents.