From what little research I've done into jumping everyone seems to say that if you jump from high enough, it doesn't matter. Anything higher than 12 stories is probably going to be fatal regardless of what you land on.
Pretty much you'll be going fast enough so when you hit water, the water can't move out of the way fast enough relative to you. Because of this you'll be hitting a surface of similar quality to concrete. This sudden stop should be enough to either kill or incapacitate you so that you drown without any awareness of it.
However it is not uncommon that people jump into deep water from just high enough to make the impact painful and land just right to get to the bottom. If there is a current present, you'll get pulled into the undertow and drown. If not you'll still probably drown, but could still survive with injury of varying severity.
Either way never was a fan of that method, so I never attempted it. Could never find the strength to jump from a height like that and I have strong thalassophobia.