The typical rocky shore is covered twice daily by the average high tide, encompassing an area of vertical rise from about 21/2 feet to about 5 feet above the mean low-water mark. An increase in plant life is observed at the upper margin of this zone and the vegetation becomes more dense at the lower margin. The plants provide more food and cover but also greater protection from desiccation (dehydration) for the animals when the tide recedes. The animals of this zone are characterized by structural and behavioral adaptations that adapt them to tidal exposure. The periwinkle-limpet association of the splash zone is also characteristic of the upper areas of the high-tide zone.