unsinkable

/AH0 N S IH1 NG K AH0 B AH0 L/
adjective
  1. 1

    Of a ship: that cannot be sunk.

    โ€œThe Titanic was said to be unsinkable.โ€

  2. 2

    That cannot be overcome or defeated.

    โ€œunsinkable optimismโ€

Source: https://en.wiktionary.org/wiki/unsinkable