My friend showed me how to spot underground water using the basic coconut method. The age old Indian tradition.

It doesn't happen to everyone. Only few get that option by birth/Samskara Jala Rekha ಇರಬೇಕು

If this technique is unique and most effective why it's not using the world. If the cost of finding water underground is this much cheaper why the hell scientific discover expensive instrument. Its all some kind of comics/superstitious according to me. Is this scientific?

I don't think there's any scientific basis to this. While using a coconut to find water may work in some anecdotal cases, it's not reliable. Wt that said, local knowledge & traditional practices sometimes align with hydrogeological principles, makng thm useful in some conditions.

Strange coincidence. My Dad just did this at one of our relatives site in Kengeri yesterday. They bored today and water was available at the same spot in 140 ft.

Last year , we drilled borewell same way :) we got 2 inch water 😊👍

How deep is the water source in Bangalore these days ?

This is 70+ km away from Bengaluru. In Bengaluru, it depends on the area. Central and South are much better. East and North are bad.

Water diviners. But I'm not sure if it works for everyone. It happens only with some people, I guess.

I used same technique when I was constructing house