Original Medicare covers an annual wellness check for me. My doctor happens to do everything he did for my annual physical (including the awful prostrate check!!!!!) meaning he also does a physical exam - which is not supposed to be included in a wellness check.
A wellness check is covered by Medicare - a physical is not. Off the top of my head, in the last 3 years I have paid ~$180, $80, and $120 for these visits. These are discounted amounts based on what Medicare allows for a procedure/test. My first visit included a shingles or pneumonia shot that wasn't covered by Medicare - that's why the higher $$. As mentioned in an earlier post, how a doctor is able to come up with a reason to have a procedure performed and then to code that procedure will determine what gets covered by Medicare.
To the OP, if you're rec diving, you just have to indicate that you don't have any physical problems. If you tell the dive op you do, you may then have to have a statement from your doctor clearing you to dive. My buddy who had a heart attack several years ago has no restrictions but carries a statement when we travel, just in case.