The only assured way of becoming a Commando is by joining as a Royal Marine and by having the motivation to adequately prepare. The average person coming out of initial Naval training is unlikely to meet the entry standards for Royal Marines by being fit enough to pass PRMC.
In fact, RN Divers who have passed PDA will probably find their fitness levels have significantly fallen after completing training at Raleigh. Most Diver recruits need to do additional phys in their own time in order to adequately prepare themselves to undergo the rigours of Diver training.
It's not there for you 'to do', it's there to commando train personnel drafted to 3 CDO BDE. From the RN ratings side that means mainly communicators and medics. It's not a jolly course you can just do because you want to. You have to be assigned for the role in 3 CDO BDE.
It's also pretty damn hard, and harder for matelots than pongos as we generally lack the green military skills that you're expected to know week 1 day 1.
I've spent time being beasted for a week or two at CTCRM Lympstone on another course, and I can tell you the bottom field is no fun at all.
In short, as a matelot the branch to go for with the highest hands of securing a place on AACC (eventually) is MA. A warfare specialist has little to no chance.
Yep, that's the usual routine as matelots will have acquired no currency in fieldcraft skills.
Truth is, although we see MAs & other branches undertake AACC when working within 3 Cdo, it is not a mandatory requirement, nor essential - as demonstrated by MA Kate Nesbitt MC.
For those interested, the RMFA, which forms day one of PRMC, includes the following criteria tests:
3 mile run, 22.5 minutes
VO2 Max, (Bleep Test), minimum Level 11
60-80 sit-ups in 2 mins (to a bleep)
40-60 close-arm press-ups in 2 mins (to a bleep)
8-16 back-handed pull-ups in 2 mins (to a bleep)
100 metre swim.
As stated, the physical fitness entry standard for Royal Marines is significantly higher than the physical fitness pass out standard required at Raleigh.