The Pacific has ocean on the far side, too
The Pacific is wide enough that some places in it have an ocean at their exact opposite point on Earth. That opposite point is called an antipode: its latitude is reversed, and its longitude shifts by 180 degrees. So a point in the western Pacific can have an antipode in the South Atlantic.
For example, a spot near 10° north, 130° east—east of the Philippines—has its antipode near 10° south, 50° west, in the Atlantic. The match is exact on a globe, even though neither location is necessarily far from land.
A straight line is a map idea, not a route
The line connecting those two points would pass through Earth’s interior, not travel across the surface. It is a way to describe their geometric relationship; no tunnel or practical journey links them. On a flat map, the pair can look especially distant because the Pacific is often split across the map’s edges.
Most places on Earth have land at their antipodes, because continents occupy only part of the planet’s surface and ocean covers the rest. But the Pacific’s enormous area means that some of its opposite points land in another ocean. At those locations, crossing the whole planet in a straight line would take you from one sea to another—not from sea to land.
