IPA: /ˈsʌbməˌrɪnər/
KK: /sʌbˈmɛrɪnər/
A person who works on or is a member of the crew of a submarine.
The submariner navigated the vessel through the deep ocean.
Submariner → It is formed from "sub-" (meaning under) and "marinus" (from Latin, meaning of the sea). The word "submariner" refers to a person who operates or serves on a submarine, which is a vessel that operates under the sea.
Think of someone who works 'under' ('sub-') the 'sea' ('marinus') — that's why a submariner is a person who operates beneath the ocean.