Recommended depth to set lights in pool under construction

[Eric OV]

I am building a new pool out of block and want to know the best depth to set the lights.  

My pool is rectangular 36' x 12' x 4.5' deep.

I plan to use 2 or 3 LEDs along the long side pointing away from the house.  Haven't decided yet.  Will be based on fixture. 

Not putting them on the short sides because I don't want to see them.

I know the minimum depth is 18" from the waterline.

Thanks.