Describe how the vertical component of the velocity of the water varies form point X to point Z?

Question

Image with a flat horizontal line with a curve on top (beg curve: X, top middle curve: Y, End bottom curve: Z)

Mark scheme Answer:

decreases from x to y
DON’T GET I thought it INCREASES
zero at y,x,z
I UNDERSTAND
increases from y to z
DON’T GET I THOUGHT IT DECREASES
positive from x to y and negative from y to z(or vice versa)
DON’T GET HOW IT COULD BE VICE VERSA

Please help and clearly explain the things I don’t understand and why.

Explain why it decreases from x to Y and increases from y to z

Answer 1

Here I've already written what I thought of the question in caps lock and the thing I dont know at the bottom.

Answer 2

I do not have your picture.

Answer 3

Y
- -
- -
- -
- -
- -
X Z

Answer 4

Y
-- -
-- --- -
- ----- -- -
-------------- -
- ----------------- -

X Z

Answer 5

...........---y----
.........-----------
......-------------------
...--------------------------
. x----------------------------z

Answer 6

It looks kinda like the last image i posted but its a curve

Answer 7

and equal on both side

Answer 8

...........---y----
.........-----------
......-------------------
...--------------------------
. x----------------------------z
is the picture