Acquit a criminal assembly found in deep water (7)

I believe the answer is:

aquatic

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'assembly found in deep water' is the definition.
I can't judge whether this definition defines the answer.

'acquit a criminal' is the wordplay.
'criminal' is an anagram indicator.
'acquit'+'a'='acquita'
'acquita' is an anagram of 'AQUATIC'.

Can you help me to learn more?

(Other definitions for aquatic that I've seen before include "Growing or living in water" , "Water-living" , "Plant living in water" , "Living in/near water" , "20 [TERRAPIN] is" .)

I've seen this clue in The Irish Times.

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