Learn Hardcore Spanish (Spain): Otra marinera escucha a su capitana y limpia el barco después de la tormenta. - Another female sailor listens to her captain and cleans the boat after the storm.

marinera is feminine singular (because it ends in -a and refers to a woman).
Therefore, otra (feminine singular) is used instead of otro (masculine singular).

So:

otra marinera = another (female) sailor
otro marinero = another (male) sailor

What exactly does marinera mean? Is it always “sailor”?

In this sentence, marinera means female sailor, someone who works on a boat/ship.

However, marinera has some other uses in Spain:

As an adjective: un nudo marinero / una técnica marinera = related to sailors or the sea.
In food: gilda marinera, salsa marinera etc. (sea-related or “mariner-style”).

Here, because it appears as otra marinera and is a person listening and cleaning, it clearly means a female sailor.

Why is it escucha a su capitana and not just escucha su capitana?

The a here is the personal a, which is used before direct objects that are people (and sometimes pets).

escuchar algo = to listen to something (no a needed).
- Escucha la radio. = She listens to the radio.
escuchar a alguien = to listen to someone (use personal a).
- Escucha a su capitana. = She listens to her captain.

So a su capitana marks su capitana as a person who is the direct object of escucha.

Is the personal a after escucha absolutely required?

With escuchar and a person as direct object, native speakers commonly use the personal a, and it sounds very natural: escucha a su capitana.

Grammatically, escuchar su capitana (without a) is possible in theory because escuchar is a transitive verb, but:

In actual modern usage, escuchar a + person is strongly preferred.
Without the a, many native speakers would find it odd or would misread su capitana as something other than a person.

For natural Spanish, especially in Spain, use escuchar a + person: escucha a su capitana.

Why capitana and not capitán?

Spanish often has masculine and feminine forms for professions and roles.

capitán = male captain, or generic/masculine-default.
capitana = female captain.

In this sentence, capitana tells us the captain is a woman. If the captain were a man, it would be:

Otra marinera escucha a su capitán…

Does su in su capitana mean “her”, “his”, “their”, or “your”? It seems ambiguous.

Su is context-dependent. It can mean:

her captain
his captain
their captain
your captain (formal usted / ustedes)

The sentence by itself does not specify whose captain it is; we only know it is someone’s captain. Context before or after this sentence would normally clarify the owner. If you need to be explicit, you can say:

la capitana de ella = her captain
la capitana de él = his captain

But in everyday speech, su capitana is usually enough and understood from context.

Why is there no ella at the beginning? Could I say Ella escucha a su capitana…?

Spanish normally omits subject pronouns when the subject is clear from the verb ending.

escucha (3rd person singular) already tells us the subject is he/she/it or usted.
Otra marinera before the verb clearly identifies the subject as a third-person singular female.

So Otra marinera escucha… is completely natural.
You can add Ella (or Ésta) for emphasis or contrast:

Ella escucha a su capitana, pero las otras no.
She listens to her captain, but the others don’t.

But in neutral narration, you usually leave the subject pronoun out.

Why is it limpia el barco and not limpia al barco?

The personal a is normally only used with people (and sometimes pets), not with things.

limpiar algo = to clean something
- Limpia el barco. = She cleans the ship.
You do not say limpia al barco, because barco is an inanimate object.

So:

a + person: Escucha a su capitana.
No a with things: Limpia el barco.

What is the difference between barco and barca?

Both refer to watercraft, but there is a difference:

barco = general word for a boat or ship (often medium or large).
It’s the standard neutral word.
barca = usually a small boat, like a rowboat or fishing boat.

In this sentence, el barco is the natural generic choice: the ship / the boat. If you specifically mean a small boat, you might choose barca.

Why is it después de la tormenta and not just después la tormenta?

When después is followed by a noun, you must use de:

después de + noun
- después de la tormenta = after the storm
- después de la cena = after dinner

Without de, it is incorrect: ✗ después la tormenta.

If you use después alone, it behaves like an adverb, not followed directly by a noun:

Primero escucha; después limpia el barco.
First she listens; afterwards she cleans the ship.

Could we say tras la tormenta instead of después de la tormenta?

Yes, you could say:

…y limpia el barco tras la tormenta.

tras and después de both mean after, but:

tras is a bit more formal or literary in some contexts, though it’s also used in everyday speech.
después de is very common and neutral.

Both are correct and natural in Spain here.

Can después de la tormenta be placed at the beginning of the sentence?

Yes. Adverbial time expressions are flexible in Spanish. You could say:

Después de la tormenta, otra marinera escucha a su capitana y limpia el barco.

This is fully correct.
Difference in feel:

Original order: focus starts on otra marinera and what she does.
With Después de la tormenta in front: it slightly emphasizes the time when all this happens.

Grammatically, both are fine.

What nuance does the present tense (escucha, limpia) have here? Is it “right now” or habitual?

The Spanish presente de indicativo is flexible. It can express:

An action happening right now:
- She is listening to her captain and cleaning the boat after the storm.
A habitual action:
- She (usually) listens to her captain and (then) cleans the boat after the storm.

With no extra context, both readings are possible. Often, learners translate it as simple present in English:
Another sailor listens to her captain and cleans the ship after the storm.

If you really want to emphasize “right now”, Spanish can also use estar + gerundio:

Otra marinera está escuchando a su capitana y está limpiando el barco…

Why is it otra marinera and not la otra marinera?

The difference is:

otra marinera = another sailor / a different sailor (non-specific, indefinite).
la otra marinera = the other sailor (a specific, known one; usually when there are exactly two or a very clear small set).

In this sentence, otra marinera introduces a new character or just says “another sailor” without making her uniquely identified in a previous pair. If the context were:

Una marinera se esconde. La otra marinera escucha a su capitana.

then la otra marinera would fit (the other one of the two).

If I want to say “Other sailors listen to their captain and clean the ship…”, how would the sentence change?

You need to make the subject and verbs plural:

Otras marineras escuchan a su capitana y limpian el barco después de la tormenta.

Changes:

Otra marinera → Otras marineras (feminine plural)
escucha → escuchan (3rd person plural)
limpia → limpian (3rd person plural)

Everything else can stay the same.