Halsman didn’t use montages or any kind of tricks; only meticulous staging, a lot of preparation, enough patience and numerous failed tries. After each attempt they had to clean the spilt water from the floor, chase the cats and ease them; sometimes, accidents would happen and Dali would get literally soaked… At last, in the 28th session, the desired effect was achieved. Art doesn’t just randomly happen.

source: http://obviousmag.org/en/archives/2009/01/salvador_dali_phillipe_halsman_surrealistic_photog.html