The Ala Kahakai National Historic Trail Waikui boat ramp is located on the island of Hawaii. It is a concrete boat ramp used primarily for launching small boats and watercraft. The ramp is approximately 20 feet wide and has a gentle slope that makes it easy for boats to be launched into the water.

This boat ramp services the Waikui Bay, which is located on the eastern coast of the island of Hawaii. This bay is known for its calm waters and is a popular spot for fishing, snorkeling, and kayaking. The body of water is also home to green sea turtles and other marine life.

The type of craft permitted on the water in Waikui Bay includes small boats, canoes, kayaks, and other non-motorized watercraft. However, it is always recommended to check with local authorities for any restrictions or regulations before launching any watercraft.

The information provided in this answer is accurate as of the time of writing, but it is always recommended to verify information with local authorities and official sources to ensure accuracy.