bwerb once bubbled...
I was under the understanding that it is possible to write-off a portion of you gear/classes once you are in training towards or acting as a "dive professional." It falls under the classification of "required equipment" to do your job. Typically, university or college class fees are also recoverable to some degree as part of advanced training towards your "occupation."
If there is any way in the world to write-off any portion of diving because of DM or DM in training status, it's well worth it.