This trophy can only be achieved once you’ve beaten the game. When you first arrive in The Stranded Sailor, you’ll notice a restaurant of the same name. It’s just past the entrance but before reaching Clever Grunt.
Inside you’ll meet Jefferson, who’ll offer you free soup, as long as you’ll lend him an ear as he waxes poetic about hidden shiny things that are still up for grabs (See  Squid Soup? for more information on this trophy). Jefferson is not the man, but the squid who resides atop him, and your ultimate goal will be to carry him from his location in The Stranded Sailor all the way to the Flooded Fortress.First thing’s first, you’ll need to turn the game from day to night. See  A True Ending for a detailed explanation of how to go about doing that.You’ll also need to collect a specific shiny thing to trigger Jefferson’s request. The shiny thing in question is the Ink-Covered Teddy Bear shiny thing. You’ll find the bear by traveling down the docks from The Stranded Sailor door and hookshotting across a gap. Consult  Ooh Shiny! if you’re having trouble locating it. Do note that you’ll have to go through a giant hammer enemy to get to it.
Bring the item back to Jefferson and he’ll ask you to carry him to his hidden secret. You’re forced to hoof it, as Jefferson isn’t too keen on using doors. Luckily, the path is pretty straightforward with very few enemies. The secret in question is located on the far right side of Flooded Fortress, not long after you exit Mushroom Dungeon. You’re looking for a moon symbol engraved on a platform and some newly spawned, translucent green platforms. It’s pretty easy to spot and Jefferson becomes very responsive the closer you get. If you’re still having trouble navigating there, check out the video below.

A Stroll With Jefferson Video Guide

After you reach the end and everything with Jefferson concludes, grab the Ancient Tablet of Knowledge and the trophy will pop.