Would this be grounds for a gender-discrimination lawsuit?

Let’s say there is a scuba dive resort in tropical waters known to be infested with sharks.
The scuba shop owner puts a policy in place: Women who are undergoing menstrual bleeding will not be allowed to scuba dive, for fear of attracting shark attacks. For that matter, nobody of any gender with an open wound or cut is allowed to dive, either.
Obviously, the owner isn’t going to (and can’t) verify if a woman is experiencing menstrual bleeding. But if a woman (for whatever reason) makes it known that she is undergoing menstrual bleeding, she won’t be allowed to dive.
Would a gender-discrimination lawsuit against such a policy be successful?

I highly doubt it would be successful. Anyone can bring a suit. I’m not a lawyer, but this is in IMHO, so I’ll offer my opinion: It’s a measure of safety for everyone involved. If it’s known that menstruation can attract sharks and attacks of divers, then the safety of the group comes before anything else. Since they don’t limit it just to menstruation, but rather any ‘open blood flow,’ you’d have a hard time proving it was discriminatory to only women.

I’m not sure.

(assuming U.S. law applies.)

You would think a rational policy to prevent shark attacks would withstand scrunity.
However, what if the shop’s policy is based on a myth. Then, perhaps, it’s a pretense to discriminate.

I will say, however, that I wouldn’t take such a case on behalf of the potential plaintiff.

No, for the same reason that amusement park rides require individuals be of a certain height or any other various policies. If it’s a safety issue, a business is expected to take all precautions to minimize risk.

There’s no federal law against gender discrimination in public accommodations, so it’s left up to the state to decide. Most states have pretty much the same law regarding a big issue like gender, though. But for all I know there’s a state out there that doesn’t even care about the other 49 and says it’s open season gender-wise.

The way this would work in the other states is the person suing has to establish that she is in a protected class and is being adversely affected by the company’s policy, to show that there’s at least some reason to believe something discriminatory is happening. That’s easy: she can say I’m a woman, and discrimination on the basis of gender is illegal, and I’m being adversely affected by this policy excluding me because of my gender. That’s a basis for a lawsuit.

The dive shop would then bear the burden of establishing a legitimate and non-discriminatory reason (LNDR) to have the policy it has. In this case, the guy would say the LNDR is the thing about the sharks, and would presumably say it’s the same policy for men who are bleeding, so look how non-gender-discriminatory it really is, after all.

If that’s a legitimate reason for the policy and the application of the policy, then we turn back to the person who filed the lawsuit. They have to now provide some evidence that the asserted LNDR is actually just a pretext for discrimination: oh, sure, he says it applies to men and women equally but look, he’s only ever applied it to women, and here’s evidence that men who should have been excluded actually weren’t.

TL;DR version: it depends.

Or, for an even closer analogy, they can prohibit pregnant riders for safety reasons. Still not gender discrimination.

Is this something you’ve encountered? This would such an unusual policy for a dive shop that I would definitely think the owner wanted to be discriminatory. Does it make any difference to the lawsuit if this is the only dive shop on the planet that feels the need for such a policy?

(Pregnancy is different. ‘Pregnant women shouldn’t dive’ is completely standard because no one knows what effect it might have on the foetus.)