So a physicist that understands boyle's law or charle's law clearly can't have a discussion about it with the instructor even if the instructor isn't explaining it well/properly?
No. Not during a class. If you think the instructor doesnt know what s/he is doing, get a different instructor or do some additional teaching to your child later. Otherwise, let him or her teach and dont stick your nose in correcting them on this and that.
The assumption that the student, even an OW student "knows nothing about diving" is simply not accurate in all cases. Perhaps in most, but far from all. By the time I started my OW class I had already read 2 books about diving and dive training and all the course material. I clearly understood the basics of diving and diving physics and could quite easily have had lengthy discussions about it with just about anyone.
Oh please. You are stretching just to try to make a point. Reading a few books on diving gives you the knowledge and ability to disagree and correct the instructor? Yeesh.
If I am teaching a course, I am responsible for the student's safety - I take it very seriously and I wouldnt be too thrilled if someone with a handful of dives decides he knows more than me b/c he's read a few books. In my experience, the "certified diver" family member is far more likely to be wrong than the instructor.
Now this is where you bring in the strawman argument of a completely incompetent instructor who would have been a safety hazard were it not for your intervention.
There's always basis for disagreeing when someone is teaching in a manner that doesn't allow you, as a student, to learn the required information. Certainly there are ways that are more and less disruptive to the classroom to air those disagreements, but to say they aren't possible or aren't valid is simply incorrect.
As I said - if you want to add to the content, do so outside the course. Dont interrupt and disrupt the class. You (I mean this generally, not specifically you) are FAR more likely to be mistaken than the instructor, assuming that s/he is competent.
I've seen it before. For example, when I teach, I have a progression in how I provide information - sometimes, I provide only the basic facts and flesh it out later. I have certain points where I let students make mistakes first and try to self-correct before I step in. I have had well-meaning friends and family jump the gun, and start providing too much information, overloading the student - or confusing them with conflicting information, etc. This throws off my teaching progression and makes it worse for the students.
If you think the instructor is not teaching properly, get a new instructor. Otherwise, let them teach and fill in whatever you think is relevant later.
V.