What is the best layer to find diamonds in minecraft?

years ago I found it very easily in layer 12, but in new versions of the game it's not so common

The best level is 11, lava is on 10 so if you shift and mine theres no way to swim in lava. Also it's the best level for mining gold, redstone, iron, diamonds. There's also a clay mining method here's link: https://www.youtube.com/watch?v=SOvfAUJ0kmk

theres a strat that uses clay in swamps that is much more efficient than strip mining

definatlely y=11. you can setup a beakon there and instamine and stay away from lava