xkcd #3251: Time Machine Conversation
Title text:
It's possible to do sea navigation without a compass, but you'll have to get some spoilers from the Polynesians.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3251/
"Lost at sea" means he gone out for fishing and never returned.
He may be out buying cigarettes for all we know.