Το απαγορευτικό απόπλου ισχύει λόγω θαλασσοταραχής.

It is a fixed, official-sounding expression meaning the sailing ban or the prohibition on departures by sea.

More literally:

• το απαγορευτικό = the ban / the prohibition
• απόπλου = of departure / of sailing

So together, το απαγορευτικό απόπλου means the ban on ships departing.

In news reports and port announcements, this is a very common phrase.

Because here απαγορευτικό is being used as a noun, not just as an adjective.

The adjective is:

• απαγορευτικός, απαγορευτική, απαγορευτικό = prohibitive / forbidden / banning

But Greek often turns adjectives into nouns when the meaning is understood. So:

• το απαγορευτικό = the ban

It is neuter singular, so it takes the neuter singular article το.

Yes. On its own, απαγορευτικός is normally an adjective meaning something like prohibitive.

For example:

• απαγορευτικό κόστος = prohibitive cost

But in certain set expressions, especially official or journalistic ones, the neuter form το απαγορευτικό functions as a noun meaning ban.

So in this sentence, it is best understood as a noun.

Because it depends on απαγορευτικό and specifies what is being banned.

This is a common Greek pattern:

• άδεια κυκλοφορίας = driving/traffic permit
• απαγόρευση κυκλοφορίας = ban on movement / curfew
• απαγορευτικό απόπλου = ban on departure by sea

So απόπλου is a kind of relational genitive: it means of departure / concerning departure.

The dictionary form is ο απόπλους, which is a formal noun meaning departure by ship, sailing, or setting sail.

In the sentence, you see the genitive singular form:

• ο απόπλους → απόπλου

This word is quite formal and is especially common in shipping, coast guard, ferry, and news language.

Ισχύει means is in force, is in effect, applies, or is valid.

It comes from the verb ισχύω.

So:

• Το απαγορευτικό απόπλου ισχύει = The sailing ban is in effect

Although ισχύω can also have the idea of be strong or have force, in everyday official language it often means:

• to be valid
• to apply
• to be in force

Because the subject is singular:

• Το απαγορευτικό απόπλου = one ban

So Greek uses the 3rd person singular verb:

• ισχύει = it is in effect

If the subject were plural, the verb would also be plural.

Λόγω means because of or due to.

After λόγω, Greek normally uses the genitive. That is why you get:

• θαλασσοταραχής = genitive singular

The dictionary form is:

• η θαλασσοταραχή = rough sea / heavy swell / sea turbulence

So:

• λόγω θαλασσοταραχής = due to rough seas

Because with λόγω, Greek often omits the article, especially in formal notices and announcements.

So this is very natural:

• λόγω θαλασσοταραχής = due to rough seas

You may also hear or read:

• λόγω της θαλασσοταραχής

That version sounds more like because of the rough seas, referring to a specific known situation.

In official language, article omission after λόγω is very common.

Θαλασσοταραχή means rough sea, heavy sea, strong swell, or sea turbulence.

It is a compound noun:

• θάλασσα = sea
• ταραχή = disturbance / agitation

So the literal idea is something like sea disturbance.

In natural English, though, you would usually translate it as:

• rough seas
• bad sea conditions

Yes, quite formal and official.

It sounds like something you would see in:

• ferry announcements
• coast guard notices
• weather-related travel updates
• news reports

A more everyday way to express the same idea might be something like:

• Δεν φεύγουν πλοία λόγω κακοκαιρίας.
  No ships are leaving because of bad weather.

But the original sentence is the standard official phrasing.

Yes. Greek word order is flexible, especially in formal statements.

For example, these are possible:

• Το απαγορευτικό απόπλου ισχύει λόγω θαλασσοταραχής.
• Λόγω θαλασσοταραχής ισχύει το απαγορευτικό απόπλου.

The second version puts more emphasis on the cause first: Due to rough seas, the sailing ban is in effect.

Both are natural.

A very natural English translation would be:

• The sailing ban is in effect due to rough seas.

Other good translations are:

• A ban on departures is in force due to rough seas.
• Departures by sea are prohibited because of rough seas.

A very literal translation such as The prohibition of departure is valid because of sea disturbance is understandable, but it sounds much less natural in English.

A simple pronunciation guide is:

To apagoreftikó apóplou ischýi lógo thalassotarachís.

Main stress:

• Το απαγορευτικό → apa-go-ref-ti-KÓ
• απόπλου → a-PÓ-plou
• ισχύει → is-CHÝ-i
• λόγω → LÓ-go
• θαλασσοταραχής → tha-las-so-ta-ra-CHÍS

That final word is long, but the stress is on the last syllable: -χής.