text: Simon Dredge suffered life-threatening injuries in the crash on Wednesday.
  He was travelling in the boat along with three other professional crew including his father Peter, a champion powerboat racer.
  Powerboat company, Vector World said the boat was on its first test run when it overturned just after 08:20 BST.
  A spokeswoman said: "We are encouraged to hear that Simon is stable and improving."
  Peter Dredge, Simon Wood-Power, a powerboat racer and Lee Hurst, a powerboat engineer were all taken to Southampton General Hospital with non life-threatening injuries.
  They have since been discharged.
  Eyewitnesses described seeing the high-powered vessel come out of the water "like a rocket" before flipping over.
  In a statement following the crash, Hampshire Constabulary said it appeared the powerboat "lost control" just before it collided with the Hamble Point cardinal mark.
  The large metal buoy marks the entrance to the Hamble River.
  A joint investigation into the crash is being carried out by Hampshire Police Marine Unit and the Marine Accident Investigation Branch.
target: A teenager is "stable and improving" in hospital after the prototype powerboat he was training in crashed and overturned in the Solent.