Down in sea where thirst cure is to be found (2,3,5)

'thirst cure is to be found' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'down in sea' is the wordplay.
I cannot quite understand how this works, but
'down' could be 'drink' (synonyms) and 'drink' is found in the answer.
'in' is found in the answer.
The remaining letters 'the' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'where' is the link.

Can you help me to learn more?