Women were allowed into the Royal Navy in 1993. Before then there was a separate service for them, the Womens' Royal Naval Service. They weren't immediately allowed into all jobs but they are allowed to apply for any job in the British military now. As far as I know each branch now has lower selection standards for women except the Parachute Regiment, Royal Marines, SAS and SBS, who have just left their standards the same, meaning that women are allowed to apply but can't pass selection. How long before they start letting women into those roles one way or another I don't know.
Note that although no women have got into the Paras, Marines, SAS or SBS, a small number have got into their helper units, for whom selection is tougher than for normal units, but still not as hard as the full selection for the elite units proper.
Anyway I'm sure it's the same in the US Navy, during your navy training you have to do firefighting/emergency repair scenarios, one of which involves carrying emergency water pumps close to the fire (in the training ship they have for these exercises) as quickly as possible. The last I heard, in the 90s like 98% of women failed this test, which obviously would be bad news in a real fire. I don't know how they've got around that, maybe made the pumps smaller or something as there are lots of women in the RN now.