Emergency services were called to Brighton Le Sands about 4pm on September 17 after two jet skis reportedly crashed.
One jet ski reportedly launched over the other and hit a female passenger.
The other driver fled the scene.
The 43-year-old woman was treated at the scene for significant facial injuries before she was taken to hospital in a stable condition.
Her injuries require ongoing treatment, police said.
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”Police are hoping to speak to a male rider of a dark-coloured jet ski that was in the area at the time of crash who may be able to assist with the investigation,” police said in a statement.
“Police have been told the rider was driving erratically prior to the collision.
“It is also unknown if the rider received any injuries in the crash.”
Anyone with information about the incident is urged to contact police.