There's no grounds to invoke HIPAA here, you're voluntarily releasing your own information to a dive shop/instructor that is not a covered entity under HIPAA.
Remember, the H and I in HIPAA stands for "Health Insurance" and the act covers people who receive payments or reimbursement related to health insurance - health care providers, health plans, and organizations that process healthcare data for healthcare providers or health plans.
I am going to have to contest this. I know of two cases personnally where HIPAA extends far beyond "Health Insurance".
The first case is from my ex-wife. The firm that she was working at, a global engineering firm, held training seminars shortly after HIPAA was passed. These seminars were to discuss, not HIPAA, but all of the personal information security laws that were made under, and as a result of, HIPPA. She told me a few of the things they discussed, and one I'll never forget - as brother-in-law was terminated from his job and they sited this new law as the reason.
My brother-in-law was terminated from his position because he asked one of his co-workers in casual conversation "How was your weekend?"
At work, you aren't even allowed to discuss personal issues, without possible reprocussions - under HIPAA.
Another one that pops into my mind; if you call off sick, unless you volunteer the information, your employer is not ask what is wrong - or for a doctors note; until, if I recall correctly, 3 consecutive days off sick. Then they can ask for a doctors note.
So yes, the HI may stand for Health Insurance, but it goes much deeper than that - ask my brother-in-law.