Circumnavigations are often spoken of in some circles in hushed tones - the pinnacle of sailing when in actual fact, a circumnav is nothing more that a large collection of "sailing from one place to the next". It's like going sailing every weekend except you leave from one place and arrive at a different place. The second trip is easier than the first and so it accrues.
String these individual trips together and suddenly, you have a circumnav. If the voyage is done right, the totally inexperienced will be somewhat experienced by the time they have to do their first ocean crossing.
Also, one shouldn't use the terms "at sea for four years" and "inexperienced" in the same sentence.
Still, Antarctica, yes well. firstly you have to have a desire to go there and if you do, you have to have large ones.
I don't have the desire so I don't have to lay claim to large ones or the lack thereof.