Crossword Genius

Kit used for exploration, primarily, in sea? (5)

Ross

I believe the answer is:

scuba

I'm a little stuck... Click here to teach me more about this clue!

This could be a double definition.

'kit used for exploration' is the first definition.
The definition and answer can be both man-made objects as well as being singular nouns.
I also know that 'exploration' relates to this answer.

'primarily in sea?' is the second definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

Can you help me to learn more?

(Other definitions for scuba that I've seen before include "Diving apparatus" , "Aqualung" , "Self-contained underwater breathing apparatus (acronym)" , "breather" , "Skin-diver's device" .)

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