I'm not sure that "iceberg" is a good metaphor for anything involving very large ships. Neither has involuntary service at sea been regarded as great idea, at least since the era of Nelson.
OK, orders are orders, if you can't take a joke you shouldn't have joined, and all that jazz. But it would be nice to see planning reflect reality, which is that recruitment and retention of people with the right talent mix is always a challenge for any organization.
That's why it's not just PC, but CS, to not maintain arbitrary bans on certain groups of people. And it's also the case that if you make the environment less desirable - if you want a future in FJs you may find yourself effectively in the RN - you either pay more or get less than you otherwise would have done. And no amount of banging on about unionist land-lubber snowflakes changes that fact.