After conducting research, I found that the boat ramp named Marina Bay in Nebraska is located on the shores of Harlan County Reservoir. The ramp is described as a modern, concrete boat ramp with a gentle slope and two wide lanes for launching boats. It is also equipped with a dock for loading and unloading passengers and supplies.

According to the Nebraska Game and Parks Commission, the Harlan County Reservoir covers approximately 13,250 acres and has a maximum depth of 70 feet. The reservoir is well-known for its fishing opportunities and is home to several species of fish, including walleye, channel catfish, and crappie.

As for the types of watercraft permitted on the reservoir, the Nebraska Game and Parks Commission allows a variety of boats, including fishing boats, pontoon boats, and personal watercraft (such as jet skis). However, all boats must comply with the state's boating regulations, including having proper safety equipment and displaying valid registration.

In terms of the width of the Marina Bay boat ramp, I was unable to find specific measurements. However, based on photos and descriptions of the ramp, it appears to be wide enough to accommodate most watercraft.

In conclusion, Marina Bay is a modern concrete boat ramp located on the shores of Harlan County Reservoir in Nebraska. It is equipped with two wide lanes for launching boats and a dock for loading and unloading passengers and supplies. The reservoir permits a variety of watercraft, including fishing boats, pontoon boats, and personal watercraft, as long as they comply with state boating regulations.