I know that the word 'sea' is uncountable. Sometimes when an uncountable word is preceded by an adjective we put an indefitite article in front of it, for example : a broad knowledge.

Can we say :

We were delighted with the view of a blue sea.

or do we have to say:

We were delighted with the view of the blue sea.

We swam in a cold sea.

We swam in the cold sea.

When we mean the movement of waves, I think we can use 'a':

It was a rough sea.

Thank you for your help,

Shadok
The seven seas.

We swam in a cold sea.< could be any sea>

We swam in the cold sea.< a particular sea>
Shadok

Can we say :

We were delighted with the view of a blue sea.

or do we have to say:

We were delighted with the view of the blue sea.

We swam in a cold sea.

We swam in the cold sea.

The choice between the definite article (the) and the indefinite (a(n)) is the choice between 'essence' and 'accident'.

If you present an essential (permanent) attribute, use the; if you present an accidental (temporary) attribute, use a(n).

We were delighted with the view of the blue sea. << The speaker believes that the sea is always blue by nature.

We were delighted with the view of a blue sea. << The speaker implies that the sea is not usually blue, or not so delightfully blue as at the time he saw it.

We swam in the cold sea. << The speaker takes coldness to be the essence (a permanent feature) of the sea.

We swam in a cold sea. << The speaker implies that the sea felt especially cold at that time.

The same choices apply to 'rough sea'.

See "[a] combing sea"

CJ

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bar9onWe swam in a cold sea.< could be any sea>
We swam in the cold sea.< a particular sea>
These interpretations seem to apply more to the countable reading of 'sea'. I think the OP was interested more in the uncountable reading.

CJ