During the escort vessel's next firing run, one of the electricians was down in the motor room, checking on possible damage. Just then a batch of depth charges arrived and exploded terribly close. The electrician came streaking it up the hatch into the maneuvering room, swearing that flames had come in through the packing glands around the propeller shafts. His shipmates pooh-poohed that possibility, but on the next run the engineer officer and two more electricians each swore they also saw flames. A scientist explained this to me by saying that undoubtedly what they saw were sound waves of frequency high enough to approach the speed of light waves. Nevertheless, Kingfish personnel, who witnessed this phenomena, still swear they saw flames.
Lockwood, Charles A., 1890-1967. Sink 'Em All; Submarine Warfare In The Pacific