The unfortunate reality is that even a young healthy individual can fall victim to cardiac arrest due to cold shock:
"In the study, published in the Journal of Physiology, they explain how rapid submersion in cold water, combined with holding ones breath, automatically activates two powerful responses in the body which may interact and cause conflict at the level of the heart."
It's the nature of the game. Should companies and private boaters alike make sure that their crew is well informed of the inherent risks? Absolutely. To not do so, in my opinion, would be classified as gross negligence.
Additionally, how many folks hit that stretch with a private or a commercial boat on a daily basis and come out the other end just fine? While my condolences go out the family, it's unfortunately nothing more than a terrible accident.