The word "海底" is formed through a direct and logical combination of its two component characters: "海" (hǎi), meaning "sea" or "ocean", and "底" (dǐ), meaning "bottom" or "base". By placing these concepts together, the compound creates a new, specific meaning that is the sum of its parts, literally translating to and universally understood as "the bottom of the sea" or "seabed". This formation relies entirely on the immediate, concrete imagery and spatial relationship conveyed by the characters in sequence.