  An apparent giant wave event having a maximum trough-to-crest height of 21
metres and a maximum zero-upcrossing period of 27 seconds was recorded by a
wave buoy at a nearshore location off the southwestern coast of Australia. It
appears as a group of waves which are significantly larger both in height and
period than the waves preceding and following them. This paper reports a
multifaceted analysis into the plausibility of the event. We first examine the
statistics of the event in relation to the rest of the record, where we look at
quantities such as maximum-to-significant wave height ratios, ordered
crest-trough statistics, and average wave profiles. We then investigate the
kinematics of the buoy, where we look at the relationship between the
horizontal and vertical displacements of the buoy, and also attempt to
numerically reconstruct the giant event using Boussinesq and nonlinear shallow
water equations. Additional analyses are performed on other sea states where at
least one of the buoy's accelerometers reached its maximum limit. Our analysis
reveals incompatibilities of the event with known behaviour of real waves,
leading us to conclude that it was not a real wave event. Wave events similar
to the one reported in our study have been reported elsewhere and have
sometimes been accepted as real occurrences. Our methods of forensically
analysing the giant wave event should be potentially useful for identifying
false rogue wave events in these cases.
