Times have consistently dropped over the years due to better training techniques and to new developments in the sport. In the first four Olympics, competitions were not held in pools, but, rather, in open water (1896– the Mediterranean Sea, 1900– the Seine river, 1904– an artificial lake, 1906– the Mediterranean Sea). The 1904 Olympics freestyle race was the only one ever measured at 100 yards, instead of the usual 100 metres. A 100 metre pool was built for the 1908 Olympics and sat in the center of the main stadium's track and field oval. The 1912 Olympics, held in the Stockholm harbour, marked the beginning of electronic timing. Male swimmers wore full body suits up until the 1940s, which caused more drag in the water than their modern swimwear counterparts. Also, over the years, some design considerations have reduced swimming resistance making the pool faster — namely proper pool depth, elimination of currents, increased lane width, energy-absorbing racing lane lines and gutters, and the use of other innovative hydraulic, acoustic, and illumination designs. The 1924 Olympics were the first to use the standard 50 meter pool with marked lanes. In the freestyle, swimmers originally dove from the pool walls, but diving blocks were eventually incorporated at the 1936 Olympics. The tumble turn, better known as the flip turn, was developed in the 1950's. The Trudgen, introduced in England during the 1880's, has been completely supplanted by the front crawl, also known as the Australian crawl. Lane design created in the early 1970's has also cut down on turbulence in water.