If you place two-block-tall-plants while holding your right mouse-button and jumping/standing in(to) the water, you may get the item dublicated and if you place the second one you get a floating sunflower-entity.

As you can see in the video the bug was catched on a private server hosted from 'Adlerauge9' on his own machine.
EDIT: Also tested in Single Player and it duplicated again

And this bug is only client-side - my buddy didn't see anything.

EDIT: Also tested without any resource pack

What I expected to happen was...:
Just placing the plant

What actually happened was...:
(Ghost-)Item-duplication + floating sunflower entity

Steps to Reproduce:
1. Drop a two-block-tall-plant
2. At least stay in the water or jump into it
3. Hold your RMB
4. Luck

_{Sorry for the bad language, we are from Germany}