Drifter performance can be degraded by the rectification of oscillatory wave motions and by windage.Rectification can occur because the drifter behaves as a damped, nonlinear oscillator forced by buoyancy, flow drag forces, and pressure gradients (Davis 1985). For
example, if the area submerged or vertical tilt of the drifter (and hence drag) depends on the wave phase, the mean drifter velocity may be nonzero even for a zeromean orbital velocity.