This is from the BBC, about sewage system of London, in which experts show the reporters around the new sewage system sewage system 0:44-0:46

We are about to go 55 meters down into the ground.

The expression "go down into the ground" caught my attention. I have been thinking about it. I wondered why he said "...go down into the ground" but not "....go down under the ground.", because they will be under the ground, just like a submarine "going down under the sea.".

Are both OK?

  • Technically a submarine doesn't go under the sea. It goes below the surface of the sea. But because prior to submarines most ships went on the surface, and people don't think much about what's under the surface (unless they are mariners, and even then they can forget to check), the inaccurate expression "under the sea" is used for under the surface of the sea.
    – Stuart F
    Commented Mar 29, 2023 at 12:52
  • Submarines are said to dive and surface.
    – Lambie
    Commented Mar 29, 2023 at 13:10

1 Answer 1


Yes, both are possible. Into the ground conveys the idea of burrowing 'into' the earth, under the ground of being below the surface.

We can speak of a submarine going down into the sea as well.

  • 1
    I completely agree with Kate's remarks but I would add: natural human language isn't very scientific. Whether we go INTO or UNDER the ground on TV doesn't reallty matter -- it only matters when you are making precise measurements on a drill. A scientist would equally understand "going MINUS 55 metres down", into the sky.
    – equin0x80
    Commented Mar 29, 2023 at 9:01

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