The blonde beauty, who has modelled for Victoria's Secret, Chanel and Marc Jacobs and hosted reality TV show Holland's "Next Top Model", is believed to be in a coma after suffering a fractured skull in the accident off the coast of the Italian island of Ischia.
The 33-year-old was helicoptered to a hospital in nearby Naples and is in a coma with a fractured skull, according to reports.
She also had injuries to her spinal cord and may be paralyzed.
Reps from Sturm's US modeling agency declined to comment.