There are strict requirements for lifejacket / buoyancy aids in the offshore oil & gas industry, requiring them to be worn when working above the water. Some places have been noted to be using a buoyancy aids rather than an auto-inflatable device. I know that theoretically this would cause them to a more sudden stop as they hit the water, increasing the danger, but I can't find any source of information that gives a clear criteria for what height should be considered dangerous.
I know there's a lot of subjectivity, since a slim person with a buoyancy aid could equate to the same force on impact as a larger person, but if we consider like-sized average adult males, one with a 150N rated buoyancy device, another with 100N, 50N and then nothing. What would the difference be?