Deep, Buoyancy & Navigation are the ones that the LDS I go through offers + 2 others that you discuss, although it’s not "mandatory" that’s the way they do it.I’ve just gotten my OW certification so I may not have a leg to stand on but in my opinion it should be, without neutral buoyancy what good are the others, if you’re doin Wreck, you don’t wanna be bounce’in off the floor and ceiling and Multi is shot as well