This synthesis is intended to be of use to bridge maintenance engineers and others concerned with the inspection and repair of bridge elements below the waterline. Problems with substructures are identified, and procedures, equipment, and techniques currently used for underwater inspection are evaluated. The methods and materials used for maintenance and repair of bridge substructures below the waterline are also described.  The report for this topic can be purchased at https://www.trb.org/news/blurb_detail.asp?id=3469