def press2depth(press, latitude):
    """ calculate depth from pressure
        http://www.seabird.com/application_notes/AN69.htm

        ATENTION, move it to fluid.
    """
    import numpy as np
    x = np.sin(np.pi / 180 * latitude / 57.29578) ** 2
    g = 9.780318 * (1.0 + (0.0052788 + 2.36e-05 * x) * x) + 1.092e-06 * press
    depth = -((((-1.82e-15 * press + 2.279e-10) * press - 2.2512e-05) *
        press + 9.72659) * press) / g
    return depth
