If the idea of making charts and the likes is what you're about then you'll love it.
A point worth noting - you may have seen WARSHIP, with all it's thousand odd ship's company... On the larger ships it's a lot less close-knit; some you'll know, a lot more you won't as everyone has a role to play and not all roles, or the people who carry them out, get to know each other. On the hydro's however, it's a much smaller team, whereby you really do have to have teamwork in you. There aren't too many ships that the oceano's and hydro's can go on, with the two most notable ones being ROEBUCK (In the Guzz a few weeks back) and SCOTT; the others being ECHO and Enterprise and the big red-hulled ENDURANCE which you'll only see if you're down about the icey places!
Not sure what anyone can say for you - the only thing that matters is if you'rei nterested in it; at the end of the day it's your life and your choice what you want to do with it. For me it's airplanes, for you it might be meteorology - just whatever floats your boat. Certainly go down to an AFCO near you and see what they're saying, even if it turns out not to be what you thought it was, atleast you'll have tried.
On the point f getting qualifications: the RN are very proactive in getting you as many pieces of paper as they can, to help you out in civvie street when you eventually leave - just passing through basic training gets you core skills or something! It used to be the case where you just learned things how the Navy taught it - the courses tend to be slightly different now, where you'll find yourself thinking "what the hell is this", "how is this applied to what I'm doing" - but it's all part of the bigger picture, and at the end, is somehow linked towards getting civilian ecognised qualifications.
All the best with whatever you choose.