An intricate universal superstructure in bifurcation sets and routes t
o chaos of a nonlinear moored ocean system subjected to monochromatic
wave excitations are investigated analytically and demonstrated numeri
cally in detail herein. System nonlinearities include complex geometri
c restoring force and coupled fluid-system exciting forces. Primary an
d secondary resonance regions are identified by employing variational
analysis techniques for local stability. Tangent and periodic doubling
bifurcations are examined to reveal the underlying intricate superstr
ucture. Numerical results of this complex system uncover a steady-stat
e superstructure in the bifurcation sets that exhibit a similar bifurc
ation pattern of coexisting solutions in the subharmonic, ultraharmoni
c, and ultrasubharmonic domains. Within this superstructure it is illu
strated that strange attractors appear when a period doubling sequence
is infinite, and when abrupt changes in the size of an attractor occu
r near tangent bifurcations.