Are women in the Navy allowed in submarines?

Historically no, women have been restricted from submarine duty for various reasons, the biggest being the sheer tightness of quarters and lack of any privacy whatsoever onboard. While females have been riding submarines for many years, they've typically been officers or civilian contractors in limited numbers for short periods.

However, the current "administration" has recently announced its intention to open submarine duty up for females. Whether it'll happen is another story - social experiments are great ideas, but in reality they don't often work in forced situations where there has been good reason not to do it. The idea of serving on a submarine is great when you don't know the extreme risks to health involved - that's why it's all-volunteer and considered hazardous duty. Also, most wives of submarine sailors have never been comfortable with the idea of females in numbers in such tight spaces (no pun intended). Most believe that for it to really work, females should have their own boat - submarines aren't like ships in that they aren't designed for mixed-gender crews. There are many who also forget that the Submarine force is all-volunteer - if they start putting females on subs, male sailors can always un-volunteer themselves real fast, forcing a major fleet resource problem. The Navy can only prolong transfers for so long - if someone doesn't want to serve on a boat anymore, they don't have the right to keep them from transferring. The likeliest scenario would be the backbone of the force, senior enlisteds, which would fundamentally cause an experience meltdown and a personnel crisis within the force itself that would take years to recover from, if it ever did. Most submariners don't think that women can't do the job - it's the cultural and psychological problem of having women in tight spaces in non-private areas for extended periods (months). Even having women riders in the past have made crews uncomfortable for the short duration of their stays, and those women were restricted to certain areas of the boat and had their own private quarters.

Fast Attacks are too tight regarding spaces and quarters, where sailors typically share a bunk (hot bunking) - one person is on watch where the other is asleep and better quarters are only afforded for senior enlisted and officers. To make such quarters available for junior females would cause a lot of discontent through the force, orders or not. They'd comply, but again, it's all-volunteer, and the job is stressful enough. The divorce rate for submarine sailors is around 70% already.

FBM submarines are likely the best place for women - they're much larger and have 6 man staterooms for crewmembers. It'll be interesting to see how it proceeds - having worked at the highest levels of the Navy and a former submariner myself, I can already see the problems ahead. Most other navies do not allow women on submarines either for similar reasons, and those that do only have Diesel-Electric submarines. Nuclear powered boats pose a lot more health risks to women, which is why the Royal Navy has strictly forbidden women from submarine duty. Health problems are common for most submariners, and it's one of the reasons it's considered hazardous duty.

One question that all prospective women should be asked before volunteering (though it'll never happen) is "Are you willing to risk losing your ability to have kids?". Nuclear submarines are one big health hazard - few crewmembers leave the service without some submarine related health problem. For me, it was Asthma and an inability to sleep properly. Others, suicide, cancer, and other things that are classified that I still can't talk about. As I said, it's easy to want something when you're not aware of all the risks, and those risks are classifed Secret and not made public.