All these structures are designed to undertake a particular function, and withstand the normal and extreme storm forces at their location. These forces they are designed for depend on water depth, exposure to swell waves, currents and may allow for unstable or changing bed condition.

Construction of offshore structures often hinges on site geological and seabed conditions and part of the design may be to adequately investigate and define the seabed structure, as seabeds vary greatly from tens of metres of soft sludge sediments to sand to hard rock. Local features such as old buried riverbeds may cause the seabed conditions to vary greatly within a short distance.

Structures offshore are generally built from materials such as steel and concrete using normal structural engineering principles, once the forces and loads on them have been evaluated.

Construction in the offshore area is particularly difficult due to the water depth and varying water conditions, and is generally undertaken by specialist contractors. The design used must be suited to methods employed by these contractors.