Crossword Genius

Sea dwellers with chambers in submarines? (10)

Ross

I believe the answer is:

nautiluses

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

This might be a double definition.

'sea dwellers' is the first definition.
Although both the answer and definition are plural nouns, I cannot understand how they can define each other.

'chambers in submarines?' is the second definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps you can see an association between them that I don't see?

'with' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times and The Sunday Times.
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