With a surface of almost 600 sq. km, Balaton is the biggest lake in central Europe. Its shallowness means it warms quickly and for 6 months of the year is a magnet to bathers. It is 77.8 km long and between 3 and 12.5 km wide. Its shoreline amounts to 195 km and the average depth is 3.14m. At Tihanyrév, the site of the North-South passenger and car ferry, the average depth is 3 m. Off Tihany, however, the lake is 12.2 m deep. Although a sea once rolled over the region Balaton now occupies, the lake is not a remnant of it but relatively young at around ten thousand years. Precipitation filled a once much larger geological depression. In comparison with many European lakes, the water of Balaton is very clean and rule number one is thus to protect it against the numerous perils of modern civilization. The strict Clean Water regulations - e.g. motor boaters must betake themselves to other waters - are appreciated by sailors, numerous sail boarders and obviously bathers. The water is often described as silky, or at any rate that is the sensation the skin conveys. This is not an illusion: the water is slightly alkaline and gentle - because of the fineness of its suspended matter and mineral particles it could as well be described as heavily diluted mineral water. The therapeutic sunbathing in the sun's rich rays, the microclimate and the non-salty but mineral rich water make bathing as enjoyable as in the sea - often from as early as May through to early autumn in October.