I was playing on a Vanilla Multiplayer Server which was a fair bit laggy. I jumped off of a high ledge with the assumption that the water would slow me down and catch me - it didn't. Instead, I kept falling and hit the floor of the river and died which produced the text "death.fell.accident.water".

I tried recreating this on Singleplayer as much as I could but to no avail so I can only assume lag was a contributing factor. I originally thought it was a new mechanic but apparently not!!!!

So I went back to the server I was on: I managed to take damage but my health wasn't low enough to die from it. I kept trying and trying and it didn't show up again. Hopefully what I have is enough proof that the string exists.

Steps to reproduce: 

1. Fall from a great height into water on Survival mode.

2. Have the water not slow you down through whatever means (probably lag).

3. Die from the fall!

4. Hope that the string is produced.