I dropped my iPhone 6s into water for about 30 seconds and now it does NOTHING..screen is black please assist

If it’s not water resistant (can’t recall if the 6s was part of the water resistant models like they are now but a quick search can get that info) then absolutely. They aren’t meant to come in contact with water. The old school suggestion has been to try drying it out in a container of dry rice but no guarantees that will work. Just depends on how much damage the water was able to cause to the internals. If that’s the case you may need a new phone or may have to see if a repair shop can do anything (3rd party because Apple won’t fix water damage).

Make a genius bar appointment with Apple for an evaluation.

They have diagnostic tools and can tell you what options you have.

One option is Out of Warranty replace,meant for a fee.