I agree a DPV is a lot more practical.
I also suspect it's just an artsy sort of film not actually a diver with paraplegia. If you look at the clip from about 3:25-3:33, she does an interesting vertical move - but controls the pitch of the plastic dive planes with her feet.
It's possible that she may have some form of dystrophy, post polio syndrome or other disability that precludes walking but might leave enough residual motion and strength to do that, but it's suspect, especially when you add in the massively impractical aspects of getting her and the chair on and off a boat compared to a paraplegic diver using a DPV or just free swimming using hands only.