Areas normally above the water in a lagoon are called barene or salt marshes and are characterised by halophilic vegetation typical of salty soils. Their height varies around the average high water mark with small differences in height and frequency of flooding determining changes in the vegetation. The plants present special adaptations such as resistance to the entry of sodium into their cells, the accumulation of sodium in the cell vacuoles and the elimination of sodium from the secretory cells present in the stem and leaves. Salt marshes and tidal flats are criss-crossed by small canals or tidal channels, of widely-varying width and depth, which channel the water towards higher land during the rising tide and towards the sea or the main channels during the falling tide.