Easy,just fail the Medical.It "might" be that you "cant " pop your ears,or have claustrophobia?Just a suggestion.Drop by your sickbay and ask a freindly MA just what the Medical entails then you might have a basis for a Plan.
Don't fight it, Go for it!
I'm an ex wafu but worked with submariners after I left the services. Finest bunch of men I ever worked and drank with. Worth going submariner just for the mates you'll make.
If you join your 1st boat as a Baby Tiff - you'll be in the JR's Mess for breakfast - get rated up and have your dinner in the SR's grot and probably end up in the Bunhouse as the MEO for supper. If the thought of serving with a bunch of very worthy people is not your bag - B&Q are advertising for trolley pushers.
In general they can spot some one working their passage pretty well, and have their ways of dealing with it. Like Janner I knew many pressed men, but very few ever tookthe otion f return to GS when it was offered. Probably the most effective way of getting out of it is to ensure yous shipmates in yur part 3 boat want rid of you, then you will almost certainly get the heave, but leave behind 100 blokes who think you are a c*nt.
I remeber a UC2 who tried to get of his bomber draft by claiming he was queerand the PV guys just laughed at him, got drafted anyway with his clearance too.