Hay mar picada durante la travesía.

Because hay is used to say that something exists or there is/there are something.

So Hay mar picada means something like There is rough sea / There are choppy sea conditions.

By contrast, está would normally be used to describe the state or location of something more specifically, for example:

• El mar está picado = The sea is rough/choppy

A useful contrast is:

• hay = existence
• está / están = state or location

Mar picada is a nautical and weather-related expression meaning choppy sea, rough sea, or agitated sea conditions.

It does not mean that the sea is literally picked or bitten, even though picada comes from the verb picar. In this expression, it is just the standard way of describing the sea when it has noticeable wave movement and is not calm.

So learners should treat mar picada as a set expression often used in ferry announcements, sea forecasts, and travel contexts.

Good question. Mar can be masculine or feminine in Spanish.

• General everyday usage often prefers el mar
• In nautical, maritime, or poetic language, la mar is also very common

In this sentence, the adjective agrees with the feminine use, so you get:

• mar picada

You may also hear:

• mar picado

depending on the speaker and context. In Spain, especially in maritime or forecast-style language, the feminine use is quite natural.

Because after hay, Spanish often uses a noun without a definite article when talking about something in a general, existential way.

So:

• Hay mar picada = there are rough sea conditions / the sea is rough during the crossing

This is similar to other weather or condition statements such as:

• Hay niebla = There is fog
• Hay oleaje = There is swell
• Hay viento = There is wind

Using la here would change the feel and would usually make it sound more specific.

Durante means during, and la travesía means the crossing, the voyage, or the journey.

In this context, because the sentence is about sea conditions, la travesía most naturally means the sea crossing or the voyage by boat/ferry.

So the phrase tells you when the rough sea happens: during the crossing.

Not exactly.

• Viaje is the general word for trip/journey
• Travesía often suggests a crossing or a journey through a stretch of space, especially by sea

In a maritime context, travesía sounds more specific and more natural than viaje. A ferry company or sea forecast is very likely to use travesía.

So:

• durante el viaje = during the trip
• durante la travesía = during the crossing / voyage

The second one fits this sentence better.

Yes. It sounds like the kind of language you might hear or read in:

• ferry announcements
• weather reports
• maritime forecasts
• travel notices

It is a slightly formal or technical way of speaking, especially because of mar picada and travesía, but it is perfectly normal in that context.

A more everyday way to say something similar might be:

• El mar está picado durante la travesía
• Habrá mala mar durante la travesía in a forecast-style context

Yes. Spanish allows some flexibility.

For example:

• Durante la travesía hay mar picada
• Hay mar picada durante la travesía

Both are correct. The version with durante la travesía first puts a bit more focus on when it happens. The original version first presents the condition itself.

Yes. Hay does not change here. It is the standard impersonal form of haber in the present.

With uncountable or mass nouns like niebla, viento, oleaje, or mar picada, Spanish still uses hay:

• Hay niebla
• Hay viento
• Hay mar picada

So learners can think of hay as a fixed form meaning there is / there are, without worrying too much about singular or plural in this specific sentence.