Regardless of Jax's claim that they are fictitious,

They were fictious when I made the claim. I said they would twist off, and
that none had been delivered to the market. The manufacturer later added
adjustable fins to the unit to keep the twist at bay. The fins need to be
adjusted for the speed at which the unit is traveling in the water to keep the
twist at bay.

Reports are now that the units need a fair amount of boat speed to work, and
that boat speed a couple knots higher pulls the units from the water.