As a result, they become stuck by their heads to rocks. They eat by kicking the feather-like feet into the water to capture plankton. They scrape algae from the rocks with their sandpaper-like tongue, or radula. Limpets and snails only graze while the tide is high. Limpets always return to the same place when the tide retreats.
Some limpets carve themselves a place in the rock which perfectly fits their shells.
This protects them from being eaten and drying up when the tide is low.