Wave height evolutions with time, showing (a) linear fractal sea surface without current; (b) linear fractal sea surface with current C0 = 0.6 m·s−1; (c) linear fractal sea surface with current C0 = −0.6 m·s−1; (d) nonlinear fractal sea surface without current; (e) nonlinear fractal sea surface with current C0 = 0.6 m·s−1; (f) nonlinear fractal sea surface with current C0 = −0.6 m·s−1.