As Katamuki said...it is best to learn from people who are passionate about underwater photography...
HOWEVER.... taking great shots underwater is NOT something you can perfect quickly through online learning...it is a practical art...and easiest learnt through observation and direct feedback from an expert.
Whilst any PADI instructor can qualify to teach this course - it is best to seek out an instructor who is passionate and educated in-depth on this subject.
There are many instructors who enjoy underwater photography as their personal hobby - and do it on a daily basis. Before you book a course, chat in detail with the instructor, ask to see their portfolio....if you like their results - then it may be a good bet to train with them.
Also, many professional underwater photographers (not instructors) run diving photography and processing workshops. You wont get a plastic card with these courses, but the technical content and feedback should be great nonetheless. Again, research the course provider first..... Of course, these courses are often far more expensive than the standard PADI specialty course...but you get what you pay for....
OF COURSE...the same is true of any PADI Specialist course.... if your instructor is an avid wreck or technical diver...then they will have more to offer if they teach those (relatively basic wreck or deep diver...) specialty courses. If they are a qualified Dive Medic, then there Rescue Courses will have added benefit. If they are a service technician, then their equipment courses will be more interesting and informative.
With any course....look behind the credentials and investigate the interests and experience of the instructor concerned.....