1 Wendy: Apprentice Bosun Higgs, ye be needin’ some bringin’ up to speed on pirate protocol.
2 Higgs: Ah, belike some sort of... Pirate Code?
3 Wendy: That be a different thing. I be talkin’ about general experience. Have ye e'er been at sea before?
4 Higgs: Me elder brother told me I was all at sea once.
4 Wendy: That not be the same thing...

While this is an amusing mix up of the literal and metaphorical meanings of "all at sea", I'm slightly saddened to have to report that it seems to be an anachronism in this comic.

According to phrases.org.uk, the term "at sea" was used literally as a nautical term up to the 18th century, when a metaphorical sense started to creep into usage. Sir William Blackstone wrote in his Commentaries on the Laws of England in 1768:

"If a court of equity were still at sea, and floated upon the occasional opinion which the judge who happened to preside might entertain of conscience in every particular case."

Of course the term was no doubt in verbal use well before Blackstone's written word. The first written usage of "all at sea" that phrases.org.uk was able to find was an 1893 usage by Frederick Courteney Selous in Travel and Adventure in South-East Africa, which sports the wonderfully verbose subtitle: Being the Narrative of the Last Eleven Years Spent by the Author on the Zambesi and its Tributaries; With an Account of the Colonisation of Mashunaland and the Progress of the Gold Industry in That Country.

"I was rather surprised to find that he seemed all at sea, and had no one ready to go with me."

So alas, we must find the metaphorical usage by 16th century British colonists in the Caribbean to be anachronistic.

Unless of course Apprentice Bosun Higgs's brother meant it literally.