How the lighting setup needs be done to create the effect of light coming from inside the water? 
thanks for your tips… 
this is my setup, hope it helps.
very nice!
looks nice. if your referring to caustics created by the water, I might stick an omni or a few right on top of the water, using a caustics looking map as a projector. if you carefully attenuate them it might look right. prolly alot of test renders involved.
I forgot, I got GI refraction and reflecion on.
i think your scene overall looks a little light for a night scene, maybe darken your environment light a bit, and maybe make it a dark orange tint
it wasn’t supposed to be night scene it was late afternoon.
Are your Omni Lights below the surface of the pool?
Thnks
yep.
Nice. How long for you to render them? and what resolutions?
Hey lukx: Very nice effect man!..
thanks to all for your answers..
It was quite big scene (huge hotel) so render times were quite big but just for swimming pool it was breeze.
no prob, glad I could help