The Whitewater River Run in Hawaii's state is an exhilarating adventure for thrill-seekers. The river run starts at the headwaters and includes all tributaries to the confluence with Pelekunu Stream. The ideal streamflow range for this river run is 200-500 cfs. The class rating for the river ranges from class II to class IV, offering a range of rapids and obstacles. The total segment mileage is approximately 5 miles, which can take up to 3 hours to complete.

Specific river rapids and obstacles that can be experienced during the Whitewater River Run include "The Toilet Bowl," a class III rapid that features a circular eddy that can trap and spin rafts, and "The Slide," a class IV rapid that features a steep drop and a tight channel. Other rapids and obstacles include "The Pinball Machine," "The S-Turn," and "The Jaws."

There are specific regulations in place for the Whitewater River Run to ensure safety and preservation of the natural environment. Only licensed tour operators are allowed to conduct the river run, and all participants must wear personal flotation devices and helmets. The number of participants per trip is also limited to ensure minimal impact on the river ecosystem.

In conclusion, the Whitewater River Run in Hawaii offers an exciting adventure for experienced rafters. With its ideal streamflow range, class rating, segment mileage, and specific rapids and obstacles, the river run promises an unforgettable experience. However, it is important to adhere to the specific regulations to ensure safety and preservation of the environment.