The book "Oceanographic Instrumentation" provides a comprehensive overview of the various instruments used at sea and the underlying principles behind their operation. It covers both traditional instruments and the latest advancements in the field. Oceanographic instrumentation poses significant challenges for both the ocean engineering and marine sciences communities. Unlike other technological fields such as aerospace, the state-of-the-technology in oceanographic instrumentation is still relatively primitive. This situation is problematic as it leads to unreliable data and wastes valuable resources like time, ships, manpower, and money. The audience for this book includes individuals involved in collecting and utilizing data from the marine environment, as well as government agencies that are major buyers and users of oceanographic instrumentation. It addresses the current problems in the field and proposes recommendations for new policies and action programs by the Federal Government to improve the state-of-the-technology and enhance the quality of oceanographic instrumentation.