Magic Conch

Two sources, both tied to the desert. Sandstone chests in the upper part of the underground desert hold it, and it also turns up in the crates you fish out of an oasis. Neither is reliable, so it is usually something you stumble into while looting the desert rather than something you go and get on purpose. The underground desert is a rough place for an unprepared character, and if all you want is a trip to the coast, walking there once is faster than clearing chests until one appears.

It sends you to whichever ocean is further away. Stand east of your spawn and you go west, stand west and you go east, so you choose your destination by walking a short way in the opposite direction first. Standing in an ocean counts too, which means a second use bounces you straight back across the map.

The exact landing spot is worked out at the moment of teleport rather than when you click, and there is a short delay in between. The game looks for the outermost tile, then the highest one, that is not sitting under water. On an untouched world that puts you on the sand at the water's edge. It also wants solid ground stacked below that tile down to sea level, though small gaps in the column are fine, which is why changing your own height with a mount can land you in a slightly different spot each time.

Only one ocean in a world can hold a pylon, so this is how you reach the other one on demand. It also solves the dungeon, which always generates nearer a coast than the middle of the map. That matters most after Plantera, when the dungeon starts killing you regularly and the walk back is the real cost of every attempt.

It makes building out a pylon network much less tedious, since you can bounce between spawn and a half finished coastal town for materials instead of crossing the world each way. The outer edges of the map are also where probes like to spawn and where the outermost celestial pillars tend to land, so it doubles as a shortcut to both. Early on it is the quickest route to the Angler if you have not explored either coast yet.

The destination has to be a real ocean with dry footing above the water. Flood both of them, or build over them, and nothing happens at all: you stay exactly where you were standing. A failed attempt still cancels your momentum, which is unpleasant halfway through a dive, though it does not eat your remaining flight time or hand back any extra jumps.

It is also one of the slowest items in the game to activate, tied with the other teleport tools, so it is travel and not an escape button. Anything chasing you will still be there when the animation finishes.

There is no cost and no cooldown, so once you have one it stays in the inventory for the rest of the run. Eventually it folds into the Shellphone along with the Magic Mirror and the Demon Conch, which collapses every teleport destination you own down to a single slot. The tooltip about hearing the ocean inside a shell, and the name itself, are lifted from a cartoon episode that became a meme long before it became an item.