Na pláži jsme viděli starou loď u moře.

Because na can require different cases depending on the meaning.

Here it means on the beach / at the beach as a location, so Czech uses the locative case:

• pláž = beach
• na pláži = on/at the beach

If there were movement toward the beach, you would usually use the accusative:

• Jdeme na pláž. = We’re going to the beach.

So:

• location → na pláži
• direction/movement → na pláž

Czech past tense is usually formed with:

• a short form of být = to be
• plus the -l participle of the main verb

Here:

• jsme = we are / auxiliary for we
• viděli = saw

Together:

• jsme viděli = we saw

The infinitive is vidět = to see.

A very useful pattern:

• viděl jsem = I saw
• viděl jsi = you saw
• viděl = he saw
• viděla = she saw
• viděli jsme / jsme viděli = we saw

In modern Czech, the short auxiliary often comes in the second position of the sentence, which is why jsme appears where it does.

Both are possible.

Czech word order is much freer than English word order, but it is not random. The short auxiliary jsme often likes to stand in the second position in the sentence.

So in:

• Na pláži jsme viděli starou loď u moře.

the first unit is Na pláži, and jsme comes right after it.

You could also say:

• Na pláži viděli jsme starou loď u moře.

but that sounds less natural in normal speech.

A very common alternative is:

• Na pláži jsme viděli starou loď u moře.
• Starou loď jsme viděli na pláži u moře.

The meaning stays similar, but the emphasis changes.

Because starou loď is the direct object of the verb viděli.

The basic dictionary forms are:

• stará = old
• loď = ship/boat

But after vidět in this sentence, the object must be in the accusative case.

Since loď is a feminine noun, the forms change:

• nominative: stará loď = an old ship
• accusative: starou loď = an old ship (as the thing being seen)

So:

• Viděli jsme starou loď. = We saw an old ship.

This is one of the most important Czech patterns: adjectives change to match the noun in gender, number, and case.

Because feminine nouns do not all behave the same way.

The noun loď belongs to a type of feminine noun where the accusative singular is the same as the nominative singular:

• nominative: loď
• accusative: loď

But the adjective still changes:

• nominative: stará loď
• accusative: starou loď

So the case is shown mainly by the adjective here.

This is very normal in Czech. Sometimes the noun changes, sometimes the adjective changes, and sometimes both change.

The preposition u means by, near, at, and it requires the genitive case.

The noun is:

• moře = sea

After u, it becomes genitive singular:

• u moře = by the sea / near the sea

In this particular noun, the genitive singular looks the same as the nominative singular:

• nominative: moře
• genitive: moře

So even though the form does not visibly change, the case is still genitive because u requires it.

They are related, but not identical.

• na pláži = on/at the beach
• u moře = by the sea / near the sea

So the sentence gives two location ideas:

• the action happened on the beach
• the ship was by the sea

In many contexts these overlap naturally, but Czech uses both expressions because they highlight slightly different things.

You can think of it like this:

• pláž = the beach area
• moře = the sea itself

Loď can mean both boat and ship, depending on context.

Czech does not always distinguish them as sharply as English does. If the exact size or type matters, Czech may use more specific words, but loď is the normal general word.

So in this sentence, starou loď could be understood as:

• an old boat
• an old ship

The best English translation depends on the context already given to the learner.

Because in Czech, subject pronouns are often omitted when they are clear from the verb form.

Here jsme already tells you the subject is we.

So:

• (My) jsme viděli... = We saw...

Usually Czech prefers to leave my out unless you want emphasis or contrast:

• My jsme to viděli, ale oni ne. = We saw it, but they didn’t.

In your sentence, my is unnecessary.

Yes, that is a good question.

In the plural past tense, Czech distinguishes:

• viděli = masculine animate / mixed group / unspecified group
• viděly = all-female group or non-masculine subjects in some contexts

Because the subject is omitted, viděli is the normal default if the group is mixed, includes at least one male, or the gender is not specifically known.

If the speakers were known to be all female, you could say:

• Na pláži jsme viděly starou loď u moře.

So the sentence as written does not necessarily focus on who we are; it just uses the common default plural form.

The verb here is from vidět, which is imperfective.

In a simple past sentence like this, vidět often works perfectly well:

• Viděli jsme loď. = We saw a ship.

Czech aspect is very important, but not every English past tense forces a different choice. In many ordinary statements of perception, vidět is the normal verb.

A perfective partner often mentioned is uvidět, which can mean something like catch sight of / come to see / notice suddenly.

Compare:

• Viděli jsme starou loď. = We saw an old ship.
• Uviděli jsme starou loď. = We caught sight of an old ship.

The second one can sound a bit more like a completed moment of noticing.

Yes. Czech word order is flexible, and changing it often changes the focus or emphasis, not the core meaning.

Your sentence:

• Na pláži jsme viděli starou loď u moře.

Possible alternatives:

• Starou loď jsme viděli na pláži u moře.
• U moře jsme na pláži viděli starou loď.
• Na pláži jsme u moře viděli starou loď.

These are not all equally natural in every context, but they are grammatically possible. English relies much more on fixed word order; Czech often uses word order to manage what is old information and what is new or important information.

A few useful pronunciation notes:

• pláži: plá-ži

  • á is a long vowel
  • ž sounds like the s in measure

• jsme

  • often pronounced something like yzmeh or smeh depending on speed and style
  • learners often find the written j surprising here

• viděli: vi-dye-lyi roughly

  • dě contains a softened d

• loď

  • ď is a soft d sound
  • the word is short but very Czech-sounding

• moře

  • ř is the famous Czech sound; it is difficult for learners
  • ře is roughly like a rolled/rising rzh sound, though there is no exact English equivalent

You do not need perfect pronunciation immediately, but it helps to notice that Czech spelling is much more regular than English spelling.