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The Marias River is a popular whitewater river run in Montana that offers an exciting and challenging adventure for kayakers and rafters. The ideal streamflow range for the Marias River is between 500 and 2000 cubic feet per second (cfs), which typically occurs in the spring and early summer months. The river is rated as a Class II-III, with some rapids and obstacles that require technical skill and precision.

The Marias River has a total segment mileage of 125 miles, stretching from the foothills of the Rocky Mountains to its confluence with the Missouri River. The upper segment of the river, from the headwaters to the Tiber Dam, is often calmer and more suitable for beginners. The lower segment, from the dam to the Missouri River, is wilder and more challenging, with steep drops and tight turns.

One of the most challenging rapids on the Marias River is the "Needle's Eye," which requires precise maneuvering through a narrow channel between two large boulders. The "S-Turn" is another difficult obstacle, featuring a sharp turn that can cause boats to capsize if not navigated correctly.

There are specific regulations to the area that need to be followed. For example, all boaters must obtain a permit from the Bureau of Land Management before launching on the river. Additionally, there are restrictions on camping, fires, and littering to preserve the natural beauty of the area.

Overall, the Marias River offers an exhilarating experience for whitewater enthusiasts, with challenging rapids and stunning scenery. However, it is important to follow regulations and safety guidelines to ensure a safe and enjoyable trip.