The elements of a bridge structure that may be located below the waterline are abutments, bents, piers, and protection systems. Bents are distinguished from piers in that they carry the loads directly to the foundation rather than using a footing.

Abutments normally do not require an Underwater Inspection, but in rare instances may be continuously submerged. Although usually founded on piles or drilled shafts, abutments occasionally rest on spread footings. Scour is almost always the primary consideration when an underwater abutment inspection is done. Local scour is often detectable during diving inspections, although sediment will sometimes refill a scour hole between the events that cause scour. More general scour, or channel degradation, will usually be undetectable to the diver and must be determined from known channel cross-sections and historical data.