El mareo termina después de la travesía.

Because mareo is a masculine noun in Spanish, so it takes el in the singular.

• el mareo = the dizziness / the nausea / the motion sickness
• plural: los mareos

There is no special logical reason it is masculine; grammatical gender often just has to be learned with the noun.

Mareo usually refers to dizziness, feeling faint, or feeling sick from motion. In context, it can often mean:

• dizziness
• nausea
• motion sickness
• seasickness, if the context is a boat trip

So the exact English word depends on the situation. With travesía, many learners will understand it as something like seasickness or travel sickness, but mareo itself is broader than just seasickness.

Related words:

• marearse = to feel dizzy / to get motion sick
• me mareo = I feel dizzy / I get travel sick

Because termina is the conjugated form of the verb terminar.

Here, the subject is el mareo, which is third person singular, so the verb must match it:

• terminar = to end
• el mareo termina = the dizziness ends

Compare:

• yo termino = I end / I finish
• tú terminas
• él/ella termina
• el mareo termina

So terminar would be the dictionary form, but the sentence needs the form that agrees with the subject.

It could say se termina, but termina is simpler and perfectly natural.

Difference in feel:

• El mareo termina = the dizziness ends
• El mareo se termina = the dizziness comes to an end / finishes off

In many contexts, termina sounds more direct and neutral.
Adding se can make it sound a bit more like the process reaches its endpoint, but the basic meaning is very similar.

Learners should know that Spanish often allows both a simple verb and a pronominal version, depending on style and nuance.

Because when después is followed by a noun, it normally needs de.

So:

• después de la travesía = after the crossing/journey
• después de comer = after eating

But if después stands alone, you do not need de:

• Te llamo después. = I’ll call you later/afterwards.

A useful rule:

• después + noun/infinitive → usually después de
• después alone → no de

Travesía usually suggests a crossing, passage, or a journey from one side/place to another. It often sounds a bit more specific than viaje.

Possible uses of travesía:

• a sea crossing
• a mountain crossing
• a difficult or notable passage/journey

Viaje is the more general word for trip or journey.

So:

• viaje = general trip/journey
• travesía = crossing/passage, often with a sense of route or duration

In this sentence, la travesía may suggest a voyage or crossing where someone got mareo.

Because travesía is a feminine singular noun, so it takes la.

• la travesía
• plural: las travesías

Also, the sentence refers to a specific crossing/journey, not just any crossing in general. That is why the definite article the idea appears in Spanish too:

• después de la travesía = after the crossing/journey

Yes, very likely.

Spanish often uses the present tense to talk about:

• general facts
• habitual situations
• things that are normally true

So El mareo termina después de la travesía can sound like a general statement: this is what normally happens.

It does not have to mean it is happening right now at this exact moment.

Yes. Spanish word order is fairly flexible, although some orders sound more natural than others.

The original:

• El mareo termina después de la travesía.

You could also say:

• Después de la travesía, termina el mareo.

That version puts more focus on after the crossing.
However, the original order is the most neutral and straightforward.

Spanish often changes word order for:

• emphasis
• rhythm
• style

But for learners, the original sentence is a very standard pattern: subject + verb + time expression

The stress is on the -sí- syllable:

• tra-ve-SÍ-a

The written accent mark on í tells you where the stress goes.

Very roughly for an English speaker:

• trah-beh-SEE-ah

In Spain, the v and b sounds are usually pronounced very similarly.
Also, because of the accent mark, -ía is pronounced in two syllables:

• sí-a, not one merged syllable

No. Mareo is not limited to seasickness.

It can refer to:

• dizziness
• light-headedness
• feeling sick from movement
• sometimes a general woozy feeling

If you want to be more specific, Spanish can also use:

• mareo por movimiento = motion sickness
• mareo en barco = seasickness on a boat

But in normal everyday Spanish, mareo is often enough if the context is clear.

Yes, in many contexts you could say:

• El mareo acaba después de la travesía.

This is also understandable and natural.
However, termina is often a little more neutral and direct for comes to an end.

Very broadly:

• terminar = to end / to finish
• acabar = to end / to be over / to finish off

In everyday Spanish, they often overlap, but they are not always interchangeable in every context. In this sentence, though, both are possible.