Nearshore shear waves (also termed FIG or far infragravity waves) are investigated. Equations governing these motions, first observed by Oltman-Shay et al. (1989) and modeled by Bowen and Holman (1989), are systematically derived using scaling arguments. The validity of these scalings is also verified, and a nondimensional parameter ϵT is identified as a possible measure of the intensity of the shear waves. This confirms the importance of the seaward facing longshore current shear, (or backshear), in determining the size and range of instability in the problem. The energy transfer between the mean flow (longshore current) and these oscillations is studied by deriving the energy equations. It is demonstrated that a necessary condition for the instabilities to grow is that the cross-shore gradient of the horizontal Reynolds stress be nonzero. This suggests the possible importance of shear waves in nearshore mixing. This analysis is then applied to two simplified longshore current-beach profiles; the first for constant depth (Bowen and Holman, 1989) and the second a more realistic sloping beach profile.