Points $R(-3,4)$ and $S(5,4)$ have the same $y$-coordinate, so the segment between them is horizontal. For a horizontal segment, the distance is the difference between the $x$-coordinates: $5-(-3)=8$. Therefore, the distance between $R$ and $S$ is $8$.

The midpoint of a segment with endpoints $(x_1,y_1)$ and $(x_2,y_2)$ is

For $A(1,4)$ and $B(7,4)$, the midpoint is

Therefore, the statement that must be true is that the midpoint of $\overline{AB}$ is $(4,4)$.

Use the distance formula between $(x_1,y_1)$ and $(x_2,y_2)$:

Substitute the coordinates $(2,3)$ and $(8,11)$:

So the distance between the fountain and the bench is $10$ grid units.

Use the distance formula between $(x_1,y_1)$ and $(x_2,y_2)$:

For the points $(2,-1)$ and $(8,5)$, the horizontal change is $8-2=6$ and the vertical change is $5-(-1)=6$. So

Therefore, the distance between the stations is $6\sqrt{2}$.

To find the point halfway between $(2,-1)$ and $(8,5)$, use the midpoint formula:

Substitute the coordinates:

So the coordinates of the water station are $(5,2)$.