Nautical Unit of Depth; to Understand Something
This page is the CodyCross answer for the clue below from Under the sea, Group 30, Puzzle 3.
Question is: Nautical Unit of Depth; to Understand Something
and the answer is: FATHOM
Word Meaning:
FATHOM — (chiefly nautical, historical, US) A man's armspan, generally reckoned to be six feet (about 1.8 metres). Later used to measure the depth of water, but now generally replaced by the metre outside American usage.
Definitions from Wiktionary.