The Navy is the best, and the Submariners are the best of the best. There he will be able to both gather and use intelligence, and do loads of tactical stuff. DH started out as a Weapon Engineer officer in submarines, has done int jobs, taught at RNEC (before it's new incarnation as a housing estate), his charge job, PJHQ (and JFHQ) and deployed with both (tri service job), 2 shore jobs in base port, directing staff on the Advanced Staff course, helped with his MA there, and then 2 in a row in Brussels.
The great thing about submarines is that they either run from Devonport or Fas Lane, so you'll hopefully be near one or the other. If he chooses the warfare branch for instance there will be more sea time than if he was a WE like my DH. If he chooses say an engineer route, then my DH had stopped going to sea by the time he was 35, apart from riding a boat on the odd occasion when he was SWEO.
As you can't go to sea with them, lots of RN people buy their own houses, and weekend when they have a shore job if necessary. It helps with your own career, and is considered quite normal not to move. I stayed in the same area for 20 years, until he got a second job out here.
The officers do loads of hands on stuff, on the basis that you can't ask your team to do something you can't do yourself; but they do also acquire other skills as well. These are important, as they go outside from 50 -55 depending on rank, and will need employment to top up the pension until they're 65. To have transferable skills, and to be able to demonstrate these is crucial, especially when competing for jobs in their 50s.
Submariners also get specialist pay to reflect the knowledge that they need that those in general service don't. This pay is also to compensate for the less than ideal conditions that they serve in. It pays for the extra washing powder needed at the end of the patrol to get the smell out of everything, even after you've hosed them down in the garden for an hour. The best way to get rid of the smell from the money is to spend it!
Good luck to you and your DH whichever service he decides to go into.