get their eyes in

[Coffee Break]

I encountered the expression "get their eyes in", but am finding it difficult to understand it. Could you please let me know what it means? Here is the excerpt:

Dick put the stumps under the breakwater and Mary piled the bathing dresses and towels together on a dry sunny heap of shingle. They simply played catch to begin with—to get their eyes in, standing round in a wide circle and throwing to one another, sometimes skiers, sometimes straight and low. Now and then Mr. Stevens, instead of throwing the ball on in the usual way, would jerk it quickly back the way it came to make the others keep on the alert, and sometimes when one of the children missed it, and had to chase it down the sands towards the sea, Mr. Stevens would rest his hands on his hips, and gaze round.

- R. C. Sherriff, The Fortnight in September, Chapter 16

This is a novel published in 1931, which describes a fortnight in September in which an English family consisting of Mr. and Mrs. Stevens, Mary, Dick, and Ernie go on a holiday. On the sands, the family are playing the catch-ball to begin with.

In this part, I wonder what this underlined expression means.
I vaguely assume that it means "to allow their eyes to adjust to the speed of the ball", but still I am not sure what it means exactly to "get" one's eyes "in", so I wanted to ask you.

 

[Tarheel]

That's a mysterious one. I have never encountered that phrase before. Normally, context would be helpful. Unfortunately, that is not the case here.

 

[dunchee]

get (one's) eye in

Definition of get (one's) eye in in the Idioms Dictionary by The Free Dictionary

idioms.thefreedictionary.com

get (one's) eye in
To improve at something, often a sport, through practice. Primarily heard in UK, Australia.
e.g. My brother devoted a lot of his spare time to football, in order to get his eye in before the big game.

(It took me a while to find it. )

 

[Tarheel]

In American English we might say they were getting warmed up.

 

[Barque]

I vaguely assume that it means "to allow their eyes to adjust to the speed of the ball",

Yes. From the reference to "stumps", it appears they were about to play a game of cricket and they started off playing catch to get their eyes used to the movement of the ball.

 

[Coffee Break]

@Tarheel, @dunchee and @Barque,

Thank you very much for the explanations and the link.
Wow, I didn't know that there was a dictionary entry regarding this expression!

So they played catch for starters, before properly playing a game of cricket, to make their eyes look at several flying balls so that their eyes may be more skillful at noticing the flying balls.

I learned a new thing all thanks to you. I sincerely appreciate your help.