Sea level rise as a result of global warming is now a widely publicized concern as strategies are currently being implemented to respond to it. However, global sea level has fluctuated by many hundreds of meters in both directions compared to current sea level, and this essay proposes to examine past and present mechanisms of sea level change and its geomorphological impacts on coasts. Before we can explain the causes of sea level change, it is important to define the different types of sea level change. Eustatic sea level, relative sea level and water depth all have specific meanings (see figure 1 below) Eustatic sea level is the global sea level and is measured between the sea surface and a fixed datum , which has always been the center of the Earth. Relative sea level is the distance between the sea surface and a local datum, such as the top of the basement rocks in a sedimentary basin. Water depth is the distance between the seabed and the surface of the sea (Coe et al 2005). The main causes of eustatic sea level change are due to changes in the volume of ocean water and changes in the volume of ocean basins. Changes in seawater volume are controlled by the formation and melting of polar ice caps and glaciers. When water accumulates in the form of ice on the Earth's surface, it causes sea levels to drop, while during interglacial periods the opposite happens and sea levels begin to rise (Pethick 1984). This is known as glacio-eustasia. In terms of the volume of water involved in this process, Pethick (1984) believes that if all the world's ice were to melt, current sea levels would rise by 40-60 metres, with Rothery (1998) and Coe et al ( 2005) suggesting it could reach a height of 80 metres. Changes in the medium of paper and bed shapes and thirdly is based on obsolete concepts (Cooper et al 2004). Global and local sea levels have varied greatly throughout Earth's history and are primarily controlled by glacioeustasy, thermal expansion, and tectonic activity. Oxygen isotope records have helped establish sea level changes in recent geological history and it is now known that sea levels in the British Isles have risen over the last 18,000 years creating the beaches and coastlines we see today. Current sea level rise is exacerbated by anthropological causes, which is a cause for concern considering the millions of inhabitants living along the coast. Predicting the geomorphological effects of sea level transgression is difficult, although the Bruuns rule of sea level change offers some, albeit limited, information on predicting geomorphological changes in the coast.