(Reuters) - Focus on sailing at the 2020 Tokyo Olympics:
THE ABSOLUTE BASICS * There are 10 events featuring four different classes of boats (skiffs, sailboards, dinghies and multihull craft). * The RS:X class are windsurfing competitions that fall under the banner of sailing. * Wind, waves and weather have a major influence on the outcome of competitions, with athletes required to make split-second judgements. * When sailing into the wind, boats use a zig-zag movement called tacking. * Boats navigate a triangular-shaped course, contending with the wind from three directions. They must pass marker buoys a specified number of times in a pre-determined order before heading for the finish line.
* Points in each race are awarded according to position and the individual or crew with the fewest total points is declared the winner.
HOW MANY MEDALS? Ten gold medals are there for the taking in five events for men, four for women and one mixed event.
WHAT HAPPENED IN RIO? Much of the focus in Rio in 2016 was on water quality as the organisers struggled to reach the targets set. There were even worries about drug-resistant "super-bacteria" in Guanabara Bay, but in the end only one of the 380 athletes complained that the water quality had affecter their performance. Britain topped the medals table, taking two gold and one silver.
WHAT CAN WE EXPECT IN TOKYO? The number of athletes has been reduced to 350, evenly split between men and women. Britain is traditionally the sport's strongest nation at the Olympics, with the United States, Norway, Spain and France also regularly on the podium. Japan acted as the host for the World Cup Series from 2017 to 2020, meaning that many of the athletes will be very familiar with their surroundings in Tokyo.
WHAT'S NEW? The biggest technological change will be seen in the Nacra 17 craft, which now have hydrofoils. These wing-like foils are mounted under the hull. As speed is increased, the hydrofoils lift the hull up and out of the water, resulting in decreased drag. A sailing hydrofoil can achieve speeds exceeding twice the wind speed.
WHEN IS IT HAPPENING? July 25 to Aug. 4
WHERE IS IT HAPPENING? Enoshima Yacht Harbour, a legacy venue from the 1964 Games which is just over 50km south-east of Tokyo.
HOW DID WE GET HERE? Known as yachting until 2004, sailing was originally supposed to be part of the 1896 Games, but the events were cancelled due to bad weather. Since then the sport has appeared at every Olympics bar 1904, which was held in the land-locked state of St. Louis, Missouri in the United States.
WELL FANCY THAT Canadian sailor Lawrence Lemieux looked set to claim a silver medal at the 1988 Games in Seoul but stopped to rescue two Singaporean sailors who had capsized and he eventually finished 23rd. The Olympic committee rewarded him for his chivalry by presenting him with the Pierre de Coubertin medal for sportsmanship.
(Reporting by Philip O'Connor; Editing by Ken Ferris)