The world is currently facing serious problems brought about by oil dependence. Reducing oil consumption provides an opportunity to increase competitiveness, technological development, and progress. Wind energy is currently the most costcompetitive form of renewable energy, and there are strong political and industrial forces (particularly in northern Europe) supporting the development of the offshore wind industry.Offshore structures may consist of a single shallow foundation such as gravitybased platforms or multiple shallow foundations acting in concert (e.g., jack-up rigs or tension leg platforms). General loading is particularly relevant in the design of shallow foundations for offshore structures because wind, wave, and current forces produce substantial lateral load components at magnitudes that are not commonly encountered onshore.Bucket foundations were pioneered in the offshore oil and gas industry and have recently been used in offshore wind turbines. The bucket foundation is a welded steel structure consisting of a tubular center column connected to a steel bucket through flange-reinforced stiffeners.The overall aim of the research presented in this thesis was to improve the design of offshore wind turbine foundations. The work was divided into two main research efforts: geotechnical engineering experiments to gain insight into the behavior of offshore bucket foundations, and development of methods to improve the study of infiltration into unsaturated soils, an important problem in geo-environmental engineering. The outcomes of the research have the potential to directly or indirectly reduce the risks and costs related to offshore geotechnics.