Based on the latest information available, the boat ramp named St. Helena - Cedar Co Access 8230 is located in South Dakota and services the Missouri River. It is situated at latitude 42.8501358 and longitude -97.27005005.

According to the South Dakota Department of Game, Fish, and Parks, the St. Helena - Cedar Co Access 8230 boat ramp is a concrete ramp that is 20 feet wide and 96 feet long. The ramp has a gentle slope, making it easy for boaters to launch and retrieve their watercraft.

The Missouri River, which is serviced by this boat ramp, is a major waterway that flows through several states, including South Dakota. It is a popular destination for boating, fishing, and other water-based activities.

As for the types of watercraft permitted on the Missouri River, it varies depending on the specific area and regulations. However, in general, boats and other watercraft such as kayaks, canoes, and jet skis are often allowed on the river. Boaters are encouraged to check with local authorities to confirm specific regulations in the area they plan to visit.

Overall, the St. Helena - Cedar Co Access 8230 boat ramp is a convenient and well-maintained facility for boaters looking to access the Missouri River in South Dakota.