Prepare your flowers for a dry spell below the surface (10)

I believe the answer is:

underwater

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'prepare your flowers for a dry spell' is the definition.
I can't judge whether this definition defines the answer.

'below the surface' is the wordplay.
'below' becomes 'under' ('under' can be a synonym of 'below').
'the surface' becomes 'water' (I can't justify this - if you can you should believe this answer much more).
'under'+'water'='UNDERWATER'

Can you help me to learn more?

(Another definition for underwater that I've seen is " Submerged".)

I've seen this clue in the Irish Times.

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