One man is missing feared dead and a second suffered a suspected broken leg following a crash between two speed boats.
Solent Coastguard received a distress call at 6.50pm from one of the vessels involved in the accident half a mile from Brighton Pier.
A fishing boat was chartered to take the man with an injured leg to an ambulance waiting at Brighton Marina.
Meanwhile, lifeboats from Brighton and Shoreham and the Lee on Solent search and rescue helicopter India Juliet were searching for a second man.
A spokeswoman at Brighton lifeboat station said body parts were found on one of the crashed boats.
Neither boat, both 25ft long, sank in the crash.
Sussex Police helicopter was also sent to the scene to search for the man overboard but was later stood down.
A flotilla of fishing boats and other pleasure craft joined in the search for the man whose hand and fingers were found on his boat.
Bini McCall, spokeswoman at Brighton lifeboat station, said: "At the moment we have our fast response boat searching together with Shoreham in-shore lifeboat and the helicopter.
"We are not sure what happened exactly but one man is missing and a second has suffered a suspected fractured leg."