Η θάλασσα φαίνεται γαλάζια το πρωί από τη βεράντα.

Because η θάλασσα is the subject of the sentence, so it is in the nominative case.

• η = feminine singular nominative article
• θάλασσα = sea

If you said τη θάλασσα, that would be the accusative form, which is usually used for a direct object, not the subject.

Φαίνεται comes from the verb φαίνομαι, which means to appear / to seem / to look.

In this sentence, φαίνεται is:

• 3rd person singular
• present tense

So it matches η θάλασσα = the sea.

The ending -εται is normal for this verb, because φαίνομαι belongs to a group of verbs that have middle/passive-style forms but can still have an active meaning in English.

So:

• φαίνομαι = I appear / I seem
• φαίνεται = he/she/it appears, seems, looks

It can mean all of those in different contexts.

With an adjective after it, as in φαίνεται γαλάζια, it usually means:

• looks
• seems
• appears

So here it means that the sea looks blue or appears blue.

If there were no adjective, φαίνεται could also mean is visible or can be seen, depending on context.

Because it agrees with θάλασσα, which is a feminine singular noun.

Greek adjectives agree with the noun they describe in:

• gender
• number
• case

Here:

• θάλασσα is feminine singular nominative
• so the adjective is γαλάζια, also feminine singular nominative

This is true even though γαλάζια comes after the verb. It is still linked to θάλασσα.

Because γαλάζια is being used as a predicate adjective, not as an adjective directly inside a noun phrase.

Compare:

• η γαλάζια θάλασσα = the blue sea
  Here the adjective is directly attached to the noun.

• η θάλασσα φαίνεται γαλάζια = the sea looks blue
  Here the adjective comes after a linking-type verb and describes the subject.

So no article is needed before γαλάζια in this sentence.

Το πρωί is a very common fixed time expression meaning in the morning or the morning.

Greek often uses the article in expressions of time:

• το πρωί = in the morning
• το βράδυ = in the evening / at night
• το απόγευμα = in the afternoon

So even though English often leaves out the article in phrases like in the morning, Greek normally includes it here.

It is in the accusative, used adverbially to express time.

This is very common in Greek. A noun phrase in the accusative can tell you when something happens.

So το πρωί literally contains the neuter accusative form, but functionally it means in the morning.

Από normally means from.

In this sentence, από τη βεράντα means something like:

• from the veranda
• as seen from the veranda
• when viewed from the veranda

So it gives the viewpoint/location of the observer, not the origin of the sea.

The full form of the feminine accusative singular article is την, but the final -ν is often dropped before certain consonants.

Since βεράντα begins with β, the usual form is:

• τη βεράντα

Both learners and native speakers often notice this pattern with τη / την.

A useful idea is:

• την is kept before vowels and certain consonants
• otherwise it often becomes τη

So από τη βεράντα is the expected form here.

It is in the accusative case, because the preposition από takes the accusative in Modern Greek.

So:

• από
  • accusative

That is why you get τη βεράντα, not η βεράντα.

Yes, but the meaning changes.

• Η θάλασσα είναι γαλάζια = The sea is blue
  This sounds like a statement of fact.

• Η θάλασσα φαίνεται γαλάζια = The sea looks blue / seems blue
  This focuses on appearance, impression, or how it looks under certain conditions.

In your sentence, φαίνεται fits well because το πρωί and από τη βεράντα suggest a particular visual impression.

Both can be translated as blue, but they are not always exactly the same in feel.

• γαλάζιος / γαλάζια / γαλάζιο usually suggests a light blue, sky blue, or azure shade
• μπλε is a more general word for blue

With the sea or sky, γαλάζια is very natural and often sounds more vivid or poetic.

Because Greek does not need a dummy subject like English it.

English often says:

• It looks blue

But Greek usually uses the real subject directly:

• Η θάλασσα φαίνεται γαλάζια

So the sentence already has its subject: η θάλασσα.

No, Greek word order is more flexible than English word order.

This version is natural:

• Η θάλασσα φαίνεται γαλάζια το πρωί από τη βεράντα.

But Greek can move parts around for emphasis, for example:

• Από τη βεράντα, η θάλασσα φαίνεται γαλάζια το πρωί.
• Το πρωί η θάλασσα φαίνεται γαλάζια από τη βεράντα.

The basic meaning stays the same, but the emphasis changes slightly.

The original order is a neutral, natural way to say it.