Open water starts causing heart attacks with those athletes with preconditions?

This clip was from a Jerry Lewis movie called Cinderfella; herein he runs up 72-steps in less than 8-seconds and suffers a mild heart attack when he steps off camera.

My mother worked on this movie behind the camera and told me all when I was child. (We still have the thank-you letter that Jerry Lewis wrote to her as well), Perhaps going from a resting state to an all out sprint could be the cause of heart attacks with those with a predisposition in place.

Note how the Escape from Alcatraz 2013 race start was conducted as an example in the second video. No acclimatization to the water, just jump sprint and go so as to get out of the way or as a reaction to the shock.