Abstract: A method and apparatus for controlling the operation of a multiple-element marine seismic pulse generating source in rough sea surface conditions. The method first determines the shape of the path along which the elements are traveling at the point in time just before each element of the source is activated. Once the shape of the path is known, the relative vertical position of each element relative to a fixed reference is determined. Adjustments can then be entered into the firing times for each element such that the primary pressure peaks constructively interfere with one another. In a preferred embodiment, a plurality of inclinometers associated with the harness from which the devices are suspended provides a tilt angle measurement from which the shape of the path can be determined and the firing times adjusted accordingly.