That was under consideration during the final year of George W. Bush's presidency. The Navy was considering an all-female crew for a Los Angeles-class attack boat. Maybe more than one, but an article linked here earlier today even identified the CO of the first all-female SSN.
The plan was to be implemented by 2009; I can only assume that it was postponed or the Navy reconsidered. You can bet that if they'd moved forward with that plan, it would've been in ALL the papers.
If that's true, the Ruskies and Chicoms had better hope they don't start trouble during the wrong time of the month.