Stone skipping
Stone skipping and stone skimming are considered related but distinct activities: both refer to the art of throwing a flat stone across the water in such a way (usually sidearm) that it bounces off the surface. The objective of "skipping" is to see how many times a stone can bounce before it sinks into the water; the objective of "skimming" is to see how far a bouncing stone can travel across the water before it sinks into the water. In Japan, the practice is referred to as "Mizu Kiri", which loosely translates to "water cutting." In "Mizu Kiri  contests, both skimming and skipping principles, as well as a throw's overall aesthetic quality, are taken into account to determine the winners. Championships and records. The Big Four" American stone skipping contests include (in order of establishment & participant rankings): (1) The Mackinac Island championship, held on July 4th in northern Michigan (entry by invite only; must win prior Mackinac Open or Pennsylvania Qualifyer to enter); (2) The Pennsylvania championship, held usually the 3rd Saturday of August in Franklin, PA - about one hour southeast of Erie (winners permitted automatic entry to the Michigan contest); (3) The Vermont championship (about one  month after Pennsylvania) on the shore of Lake Paran, North of Bennington; (4) The Great Southern championship in Arkansas (Labor Day weekend). Also notable, Coleman-McGhee founded the North American Stone Skipping Association (NASSA) in 1989 in Driftwood, Texas. NASSA-sanctioned world championships were held from 1989 through 1992 in Wimberley, Texas. The next official NASSA World Championship is expected to be held at Platja d'en Ros beach in Cadaqués, Catalonia, Spain.. A stone skimming championship takes place every year in Easdale, Scotland, where relative distance counts as opposed to the number of skips, as tends to be the case  outside of the US. Since 1997, competitors from all over the world have taken part in the World Stone Skimming Championships (WSSC) in a disused water-filled quarry on Easdale Island using sea-worn Easdale slate of maximum 3" diameter. Each participant gets three throws and the stone must bounce/skip at least twice to count (i.e. 3 water touches minimum). The WSSC for 2020 and 2021 were cancelled due to coronavirus concerns. Other domestic distance-based championships in the UK are currently the Welsh and British, but they were cancelled in 2020 & 2021 for reasons including the COVID-19 pandemic . Japan holds competitions where both skimming and skipping principles, as well as a throw's overall aesthetic quality, are taken into account to determine the winners. At present, there is also a competition at Ermatingen in Switzerland and occasionally in the Netherlands (both skimming/distance-based). The world record for the number of skips, according to the "Guinness Book of Records", is 88, by Kurt "Mountain Man" Steiner (b. 1965). The cast was achieved on September 6, 2013, at Red Bridge in the Allegheny National Forest, Pennsylvania. The previous record was 65 skips, by Max Steiner (no relation to K.  Steiner), set at Riverfront Park, Franklin, Pennsylvania. Before him, the record was 51 skips, set by Russell Byars on July 19, 2007, skipping at the same location. Kurt Steiner also held the world record between 2002 and 2007 with a throw of 40 skips, achieved in competition in Franklin, PA. The Guinness World Record for the furthest distance skimmed using natural stone stands at 121.8m for men, established by Dougie Isaacs (Scotland), and 52.5m for women, thrown by Nina Luginbuhl (Switzerland). These records were made on the 28th of May 2018 at Abernant Lake, Llanwrtyd Wells, Powys, Wales . Men's World Skimming Championship winners by year. "2020 and 2021 Championships cancelled due to aspects of the COVID-19 pandemic." Women's World Skimming Championship winners by year. "2020 Championship cancelled due to the COVID-19 pandemic." Scientific explanation. An early explanation of the physics of stone-skipping was provided by Lazzaro Spallanzani in the 18th century. The stone generates lift in the same manner as a flying disc, by pushing water down as it moves across the water at an angle. Surface tension has very little to do with the physics of stone-skipping. The stone's rotation acts to  stabilize it against the torque of lift being applied to the back. Research undertaken by a team led by French physicist Lydéric Bocquet discovered that an angle of about 20° between the stone and the water's surface is optimal to produce the highest amount of skips. Bocquet and his colleagues were surprised to discover that changes in speed and rotation did not change this fact, as it allowed the stone to be in balance and to continue with a straight and uniform movement due to the gyroscopic effect. Work by Hewitt, Balmforth and McElwaine has shown that if  the horizontal speed can be maintained, skipping can continue indefinitely. Earlier research reported by Bocquet calculated that the world record of 38 rebounds set by Coleman-McGhee, unchallenged for many years, required a speed of 12 m/s (25 mph), with a rotation of 14 revolutions per second. In popular culture. The lead character of the 2001 film "Amélie" skips stones along the Canal Saint-Martin in Paris as a plot point, and picks up good skipping stones when she spots them.