The Riverland Dinghy Derby was started in 1981 by two friends who had a bet over who had the fastest dinghy or as they call them in Australia a tinnie (or tinny). The race series has since grown popular enough to attract Red Bull sponsorship and nice cash prizes.
The boats use a single outboard engine ranging in power levels from 10 hp to 30 hp. The engine has to naturally aspirated with the more powerful classes engines are allowed to have head work along with custom props. The classes are 15 hp, 25 hp, and 30 hp standard, 30 hp super standard, 30 hp rookies, 30 hp sports, and 300 cc modified.
In the 30 hp classes the boats can reach top speeds of 49 mph (80 kph). That may not sound too fast but doing it in small open boat with no safety restraints traveling inches from trees makes it a ridiculous speed. All racers are required to wear full-face helmets and life jackets. You can see in the video below why helmets are required.