Vyplujeme, ledaže je před námi peřej.

Vyplujeme is the 1st person plural future form of vyplout, so it means we will set sail / we will sail out / we will depart by boat.

A useful detail is that vyplout is a perfective verb. In Czech, perfective verbs do not have a true present tense for present-time actions; their “present-looking” forms usually express the future. So:

• vyplujeme = we will set sail
• not we are setting sail

Because Czech often leaves subject pronouns out when the verb ending already shows who is doing the action.

In vyplujeme, the ending -eme tells you it is we.

So:

• Vyplujeme. = We will set sail.
• My vyplujeme. = also possible, but my is added only for emphasis, contrast, or clarity

English needs we, but Czech usually does not.

Ledaže means unless or sometimes except if.

In this sentence, it works like:

• Vyplujeme, ledaže je před námi peřej.
• We’ll set sail, unless there is a rapid ahead of us.

It is correct and natural, but it can feel a bit more formal, literary, or stylistically marked than very plain everyday alternatives.

Common alternatives are things like:

• pokud není... = if there isn’t...
• jestli není... = if there isn’t...

So ledaže is definitely useful, but it is not the only way to express this idea.

Because ledaže introduces a subordinate clause, and in Czech subordinate clauses are normally separated by a comma.

So the structure is:

• main clause: Vyplujeme
• subordinate clause: ledaže je před námi peřej

That is why the comma is required:

• Vyplujeme, ledaže je před námi peřej.

Because the rapid is being treated as a present existing situation: it is ahead of us now.

So the idea is:

• We’ll set sail, unless there is currently a rapid ahead of us.

If you used bude, that would shift the meaning more toward a future situation:

• Vyplujeme, ledaže bude před námi peřej.

That is grammatically possible, but it suggests unless there will be a rapid ahead of us, which is less natural in a context where the speakers are already looking at the river ahead.

So je fits well if the obstacle is understood as something already there.

Námi is the instrumental plural form of my (we/us).

It appears here because the preposition před takes:

• instrumental for location: in front of / before
• accusative for motion toward: to in front of

Here it is a location, not movement:

• před námi = in front of us / ahead of us

So:

• je před námi peřej = there is a rapid ahead of us

This is a very common Czech pattern:

• před domem = in front of the house
• před námi = in front of us

Here peřej is in the nominative singular, because it is the grammatical subject of je.

So in:

• je před námi peřej

the noun peřej is the thing that is there.

Peřej means rapid or whitewater rapid. It is a feminine noun.

Also, Czech has no articles, so peřej can mean:

• a rapid
• the rapid

The exact English choice depends on context.

Both are possible, but Czech word order is more flexible than English and often depends on what is being presented as new information.

In this sentence:

• ledaže je před námi peřej

the clause sounds a bit like an existential statement: unless there is a rapid ahead of us.

The noun peřej comes late, which helps present it as the important new fact.

You could also say:

• ledaže před námi je peřej

but that sounds less natural to many speakers in this context.
A very natural alternative would be:

• ledaže je před námi nějaká peřej
• ledaže před námi bude peřej in a different context
• ledaže je před námi peřej is fine as given

So the main point is: Czech word order is not fixed like English word order, and this version highlights the existence of the rapid.

Yes, in effect.

English often says:

• there is a rapid ahead of us

Czech does not need a separate dummy subject like there. It simply says:

• je před námi peřej
• literally something like is ahead of us a rapid

So when translating into English, you often add there is, even though Czech has no separate word for that here.

Yes. A common everyday alternative would be:

• Vyplujeme, pokud před námi není peřej.
• Vyplujeme, jestli před námi není peřej.

These mean roughly:

• We’ll set sail if there isn’t a rapid ahead of us.

That is close in meaning, but not exactly the same structure as unless.

Compare:

• ledaže je před námi peřej = unless there is a rapid ahead of us
• pokud před námi není peřej = if there isn’t a rapid ahead of us

They are near-equivalents in many contexts.
Ledaže is more compact and slightly more formal or literary.

Peřej is approximately pronounced pe-rezh.

The hardest sound is ř, which is a specifically Czech sound. It is often described as something between:

• r
• and zh (the sound in measure)

So peřej is roughly:

• pe as in pet
• řej with that special ř sound plus ej like ay in say

A rough learner-friendly approximation is:

• pe-rzhey

but that is only an approximation.

A few pronunciation notes for the whole sentence:

• Vyplujeme → stress on the first syllable: VY-plu-je-me
• ledaže → LE-da-že
• před námi → PŘED ná-mi
• peřej → PE-řej

And remember: Czech stress is usually on the first syllable of each word.

It can be used more broadly for setting off by boat or putting out onto the water, not only for a large ship leaving a harbor.

So in a sentence about a river and a rapid, vyplujeme still makes sense: the speakers are about to set off / push off / sail out.

Depending on the exact situation, English might translate it in different ways:

• we’ll set sail
• we’ll head out
• we’ll push off
• we’ll depart

The Czech verb itself is normal here.