Reports of a person in the water prompted an overnight search off Ryde.
Searches are continuing this morning (Friday), HM Coastguard said.
Coastguard teams from Ventnor and Bembridge were called at around 1am.
Ryde Rescue 2 Independent Lifeboat and Gosport Independent Lifeboat also assisted.
A search has been focussing on an area off Ryde Pier.