Nic Marillier said she took the video from Halls Head while dolphins were swimming in the area.
"The stupidity of the speed while dolphins were in the same location," Ms Marillier said. "You can hear the girl screaming."
The video attracted plenty of interest when it was posted on Facebook on Thursday morning.
"Does anyone ever do eight knots through that section?" Tom Elliott questioned. "I'm guessing not many. They'd make a fortune if they had speed cameras there. It was a glass off though, I can understand the temptation but yeah, not good form."
According to the Department of Transport, an 8-knot speed limit applies in most of the area in which the hoons were spotted.
As of December 2020, there has also been a reduced speed limit of five knots from the entrance to the Mandurah Estuary extending to the old Mandurah Bridge, including Mandjar Bay.
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