Concrete is the most common type of material encountered in Underwater Inspections, followed by timber, steel, and masonry. Common defects in concrete substructures include cracking, spalling, laitance, and honeycombing. Minor or even moderate damage to concrete can be tolerated if it does not endanger the reinforcing. Corrosion of the reinforcing can lead to serious difficulties

Timber has frequently been used for piles, especially in fenders or protection systems. The most common type of damage to timber members is from biological organisms, such as fungus, insects, and marine borers. Timber is usually treated to control infestations. In time, the treatment may leach out of the wood or the treatment layer may be penetrated. Pay particular attention to the area of the waterline and the vicinity of connectors where this type of damage may occur.