Like Metzger, Manny Di Presso is both a lawyer and an actor. Metzger tells Oedipa that Di Presso was hired to play him in a television pilot, but we later find out that the pilot was not a success and that Di Presso has gone back to practicing law. The reader is also led to believe that Di Presso suffers from paranoia.
Di Presso appears on the dock wearing a scuba suit and hiding under a blue tarp when Oedipa, Metzger, and the Paranoids travel to Fangoso Lagoons for a day trip. It turns out that he is running from his client, Tony Jaguar, who is a member of the Sicilian mafia and who wants to borrow money from him to pay gambling debts. Yikes.
Di Presso then tells Metzger that Jaguar is suing the Inverarity Estate. Di Presso tells an elaborate story detailing how his client dredged up the bones of American GIs from a lake in Italy and then sold them to Inverarity to be used in cigarette filters. Inverarity never paid Jaguar. After telling the story, Di Presso sees some of Jaguar's men coming after him and hops onto a boat to get away, leaving Metzger, Oedipa, and the Paranoids stranded at the resort.
Di Presso only appears briefly in the novel, and his main function is to tell the story of Tony Jaguar and the massacred American GIs. At the time, Di Presso appears even crazier than everyone else in the book… but this absurd scene anticipates the direction in which the book is headed. His name is a simple pun on "manic depression."