Whitewater churns into foam as double-ended paddles windmill one-person boats into position. The paddles go up in the air as the boats slide through red or green gates, then the furious wind milling begins again.
For a sport that doesn't get the attention of some of the more well-known ones, whitewater canoe and kayak has plenty of action and drama.
A few things to look for in whitewater canoe/kayak at the Rio Olympics next month:
THE LOWDOWN: The four canoe/kayak slalom events will be held Aug. 7-11, with medals award the final three days. Men compete in single and double canoe, along with kayak. Women compete in kayak only. The races will take place at the Whitewater Stadium in Deodoro on a steep 250-meter course that has between 18 and 25 gates. Green gates are negotiated with the current, red against it. Paddlers are assessed a two-second penalty for hitting a gate and 50 seconds for missing one completely.
EUROPEAN DOMINANCE: European countries have dominated the sport since its inception at the 1936 Berlin Olympics and show no signs of letting loose of their stranglehold. In men's canoe slalom (C1), European counties have won every medal but one since the 1992 Barcelona Games, when the sport was put back into the Olympic program after a 20-year absence. Europe has accounted for all but one medal in kayak (K1) and 16 of 18 medals in two-person canoe (C2) during that span. Women have had a little better chance breaking through the European stronghold, with paddlers from the U.S. and Australia combining for six of the 18 medals since Barcelona.
AMERICAN MEN: The United States team has two paddlers with solid chances to earn medals in Rio. Kayaker Michal Smolen, who emigrated from Poland as a child, was unable to compete at the 2012 London Games due to a delay getting his his citizenship, but should make a strong run to the podium this time around. Smolen earned bronze at the 2015 world championships and has times that compare to the best paddlers in the world. Not bad for someone who was terrified of the water when he first started kayaking at 8. Canoeist Casey Eichfield will be competing in his third straight Olympics and will try to pull off a double, competing in C1 and C2 with Devin McEwan. Eichfield finished fourth at world championships and was in the top 15 his previous two Olympics.
NEE'S RELIEF: Women's kayaker Ashley Nee had a rough road to her first Olympics. She qualified for the 2008 Beijing Games, but injured a shoulder during a test event and wasn't able to completely recover in time for the Olympic trials, finishing fourth. Nee had enough points to qualify for the 2012 London Games, but was edged out by Caroline Queen on a tiebreaker. Nee won the Olympic trials this May, yet still didn't have a spot secured; she had to await a decision by the International Canoe Federation to award the United States an additional athlete quota spot. Now at 27, she's headed to her first Olympics.
C1 OPENING: Men's single canoe has been dominated by two paddlers the past five Olympics: Michal Martikan of Slovakia and France's Tony Estanguet. Starting with the 1996 Atlanta Games, those two won every gold medal in C1; three by Estanguet and two by Martikan. There will be a different champion in Rio after Estanguet retired and Martikan, the only canoe slalomist to win five Olympic gold medals, failed to make the Slovakian team for Rio.
KEEP AN EYE ON: Kayaker Jiri Prskavec of the Czech Republic is the type of paddler who could be uncatchable if he's on his game. His father, Jiri, was a two-time Olympian and the younger Prskavec has a chance to make bigger waves in Rio. He was the 2015 world champion and has five medals in world championship competition.