I should have taken a picture, but I didn't think of it.

I was boating along in my sinking boat (fixed) and I saw something in the distance that looked like a layer of blocks or something someone had built. Since this was a new world generated only moments before, it could only have been Herobrine doing stuff in un-loaded, never before been rendered chunks.
When I got close, it was a 16x16 patch of kelp tops that had generated on top of the ocean surface at Y=63. I was able to punch the kelp and recieved kelp fronds as might be expected from it having grown normally. Also of note was that there was nothing seeming to hold up these tops, no connected kelp roots or stocks, only water.