Underwater Acoustics: A Linear Systems Theory Approach is an interdisciplinary and approachable textbook dedicated to the subject of underwater acoustics as well as its applications and research. The book, after giving an introduction and background discussion on underwater topics, covers specific areas such as the fundamentals of linear, space-variant, and time-variant filters; complex apertures; and linear, planar, and volume arrays. Also covered in the book are topics such as signal processing; wave propagation in inhomogeneous media; and random ocean medium transfer functions. Because of its interdisciplinary approach, the text is applicable for students in the fields of electrical engineering, ocean engineering, acoustics, and oceanography who are interested in underwater acoustics and sonar systems engineering.