First of all, it is illegal to set an age requirement for maritime captains or other personnel, according to lawyers I have consulted with. You can do this for airline pilots, but there is a specific CFR that allows for that.
Second:
Physical requirements are a function of lawsuits. The more lawsuits a company is exposed to, the more stringent will be their physical requirements, and the more prominently they will advertise them.
A certain percentage of lawsuits are bogus, based on a pretext: "Nobody told me that I would have to do X. I did it. Now I am crippled.” So companies remove the pretext for litigation by listing every possible thing a crew member must do. That’s what our lawyers advise us to do. And it works very well. It scares off people with actual physical weakness, as well as removing the pretext for the scammers.
Physical exams are a whole other thing. I hire people. Long ago we required physicals but I dropped the requirement, because not once in six years did an applicant fail a physical, except for bad teeth. And this for what was then an unusually rigorous job physically.
Why did no one fail? First, you can eyeball an applicant and in a few minutes see if they are in bad shape. If they get winded just going up the gangway during a boat tour as part of the interview, they’re not fit to work cargo in the Aleutian Islands, so you simply don’t pick them. So, the doctor only examined people in reasonable shape.
Secondly, a doctor told me he wasn’t going to risk a lawsuit from the candidate for failing them for some medical issue that had a low probability of occurring. To do that the doctor would need to cover their ass with a battery of exams that would costs $1,000s per applicant, something only the biggest vessel operating companies are going to do. So the doctor just passed them–except for bad teeth.
We stopped requiring physicals, and after 20 years I can say there was never a case where I wish we had given a physical. And this is for a job physically harder than some maritime jobs.
Big companies continue doing physicals, in part, to avoid excessive financial risk because of previous medical conditions. If someone has a heart attack aboard the vessel, the company pays for the care regardless. But if it is a congenital condition disclosed in the physical, the company can’t be blamed for the heart attack, so the impetus for litigation is reduced.
That’s why most maritime companies have you fill out that long medical history form on hiring. They’re not trying to weed you out. They’re getting an inventory list of your physical deficiencies. If you later try to sue for a heart attack, but listed a congenital heart defect, you have little pretext for litigation. Ditto, if you know you had the defect, but failed to disclose it on the form, and it was subsequently uncovered during discovery. The company pays for the medical care in any case. They are just trying to reduce the costs of litigation.