A player falls slower than normal in a flowing water column when it's surrounded by air blocks.

What I expected to happen was...:
To keep the same speed all the way down

What actually happened was...:
As I reached the area surrounded by air I slowed to a crawl, then speeded up a little just as 1 side of the flowing water column reached a wall of rock and back to normal falling in flowing water speed when the players head is level with the same rock wall.

Steps to Reproduce:
1. Default World
2. Use a flowing water column with walls around it leading to an open area and back into an enclosed flowing water column.
3. Drop and watch...

randomTickSpeed was unchanged from the default, doFireTick was disabled.

video clip of bug added with F3 shown and yes as well as visually slowing the y axis counter slowed down in the area mentioned as well.