What bay, about 1 mile wide, extends NE for about 5.5 miles and has deep water except for a very shallow expanse in the upper section?

The correct answer is Black River Bay. This bay is well-known for its significant width of about 1 mile and extends northeastward for approximately 5.5 miles. One of its notable features is that it generally has deep water, making it suitable for various boating activities; however, there is a shallow expanse in the upper section of the bay, which can affect navigation in that area. This distinct combination of deep and shallow water characteristics defines Black River Bay, making it an important and recognizable geographical feature in the region. Understanding these features is crucial for safe navigation and knowledge of local waterways.

Other bays mentioned have different geological characteristics or do not meet the specific dimensions outlined in the question, leading to their exclusion as the correct answer.