tip of the iceberg

A photomontage of what a whole iceberg might look like. The term tip of the iceberg refers to the fact that only a small portion of a floating iceberg is visible above the water line.

From the fact that floating icebergs typically have about nine-tenths of their volume below the surface of the water. Early 20th-century uses of the term are believed to have been influenced by the sinking of the R.M.S. Titanic on 15 April 1912 after it struck an iceberg.[1]

• (Received Pronunciation) IPA^(key): /ˈtɪp əv ðiː ˈaɪsbɜːɡ/
• (General American) IPA^(key): /ˈtɪp əv ði ˈaɪsbɝɡ/
• Hyphenation: tip of the ice‧berg

tip of the iceberg (plural tips of icebergs or tips of the icebergs) (plural rare)

1. (idiomatic) A small indication of a larger possibility; a problem that is much bigger than it seems.

   This is only the tip of the iceberg. Our time together can become much more exciting.

   • 2014 September 23, “a teacher”, “Choosing a primary school: A teacher’s guide for parents”, in Katharine Viner, editor, The Guardian‎, London: Guardian News & Media, ISSN 0261-3077, OCLC 229952407, archived from the original on 25 March 2019:

     Sats don't reflect the bigger picture; rather the tip of an iceberg in the only subjects that politicians think matter.

• scratch the surface

• tip of the iceberg (disambiguation) on Wikipedia.Wikipedia
• “the tip of the iceberg” (US) / “the tip of the iceberg” (UK) in Oxford Dictionaries, Oxford University Press.