The whales were built at 1/4 scale and were about 16 feet long ( nearly 5 metres). The director of the movie, Richard Thorpe did not like the look of any particular species of whale so they made a composite creature using all the features he liked from various whales. The effects department then dubbed the whale Thorpy Dick.
The model creatures were pulled around the tank using cables motivated by powerful winches. Underwater ramps supplied the diving and surfacing action. A specially rigged tail section was employed for the miniature process plate where the full size boat gets up ended. At one point a cable jumped off its pulley and cut the whale in half. The camera was shooting, depending on the shot, at 72 and 60 frames per second.
Source: The wizard of MGM, Memoirs of A.Arnold Gillespie published by Bear Manor Media.
