An 11-year boy died and his brother suffered severe injuries when they were trapped underwater for an extended period after a raft their family was in capsized on the Intamin rapids ride. Source
Accidents
Theme parks and roller coasters are statistically very, very, very safe. Out of the millions of people who ride the thousands of rides every year, there are only a small handful of incidents. You are statistically more likely to be involved in an accident driving to an amusement park than having one at a park. The rarity of accidents is one reason why the media report them, similar to plane crashes.
Every important element of a ride is inspected on a regular basis and every ride is tested every day without passengers before it opens. A ride might not open, or a safety system might activate, if there is an imperfection. For theme parks to operate, they must obtain insurance and one stipulation is their rides are frequently inspected and signed off by a strict Health & Safety governing body. Every theme park does what they can to prevent accidents because the negative press would be bad for business.
Having said all that, theme park accidents still happen…
El Toro, Six Flags Great Adventure, New Jersey, USA
Saw Mill Log Flume, Six Flags Great Adventure, New Jersey
Two people were hospitalized after a boat in the Arrow Dynamics log flume ride tipped up on an angle on the side of the flume, but did not overturn. Source
The Voyage, Holiday World, Santa Claus, Indiana, USA
During the Holiwood kNights event a 47-year-woman riding the Gravity Group wooden coaster returned to the station unresponsive and was taken to hospital, where she died. The cause of death was later determined to be a torn artery causing severe internal blood loss. Source
Flying Chair, Shaoyang Park, Hunan, China
A Star Flyer knockoff swing ride fell to the ground leaving 16 guests injured, including three in serious condition. Source
Kiddie Carousel, Balneario Camboriu, Santa Catarina, Brazil
A 13-year-old boy died after being electrocuted at a fairground when he came in contact with a children’s trike carousel that was undergoing pre-opening tests. Source (in Portuguese)
Kraken, Yupie! Park, Praia Grande, Sao Paulo, Brazil
A 19-year-old woman was injured when one of the octopus/polyp ride’s arms came loose as the attraction cycled, causing the woman to fall. Source (in Portugese)
The Hangover, Cairns Showgrounds, Queensland, Australia
Boudewijn Seapark, Sint-Michiels, Bruges, Belgium
The head of technical services died while working on an electrical box near the park’s seal enclosure. The 26-year-old man is believed to have been electrocuted after touching a live wire. Source (in Dutch)
Taitaishan Theme Park, Taiyuan City, Shanxi, China
At least 13 people died when a fire engulfed an exhibition hall of ice lantern and snow sculptures, while another 15 people were injured and taken to hospital in stable condition. Source