In that it's a free Day-One Eye Patch being sold in-game for 1 gold piece at the clothing store. A perfect joke that is perfectly Sea of Thieves and Rare. One that was born from a reddit post
by user Jefabell a few weeks ago, with the in-game description noting "A message in a bottle from Jolly Jefabell washed ashore. Eye patch makers read it and said 'aye'."
Sea of Thieves is now available to play on Xbox One or Windows 10, with full cross-play support.