It is not taught from that depth in an OW course, but there have been programs in the past that have taught it from 30 meters. If you are not sure you can do a CESA from your depth, you do a buoyant ascent, which is only different in that you do not try to control the rate of ascent, meaning you usually drop your weights. Submarine escapes using this method have been done in the 90-100 meter range. The only skill involved is exhaling fully first, then continuing to exhale all the way to the surface.