A recent article on supernovae began with:
A little under three million years ago, a massive star exploded in our galaxy about 300 light years away. This supernova was so close to our planet that, depending on where it went off, our evolutionary ancestors might have seen it as a bright light in the sky. As our solar system traveled through radioactive specks of stardust left over from the explosion, some of the dust broke through our atmosphere and rained down on our planet.
Now a recent find from deep within our still-vast ocean is helping us piece together details of a cosmic event that may have changed our planet millions of years ago.
That last sentence has me scratching my head. The oceans are of course vast, but what is the author implying by using the phrase "still-vast"?
The meaning of "recent find within our vast ocean" is clear - the ocean was, is, and will continue to be very large. So unless the author is just wasting wasting ink, still-vast must mean something different. Compare and contrast the meaning of still-vast with vast alone. Possibilities include the ocean is expected to become less large, the ocean has already become somewhat less large but is still very large (as ab2 says, this doesn't fit with reality), the ocean is expected to become less unknown (more explored), or something else.