Bølgerne er højere i dag, så vi sejler ikke ud.

Because -ne is the definite plural ending in Danish.

• bølge = wave
• bølger = waves
• bølgerne = the waves

So Danish often puts the equivalent of the at the end of the noun instead of using a separate word.

In Danish, the definite article is usually attached to the noun as an ending.

So instead of saying something like the waves with a separate word, Danish says:

• bølgerne = the waves

This is very normal in Danish. A separate definite article can appear in some other structures, especially with adjectives, but not here.

Højere is the comparative form of høj.

• høj = high / tall
• højere = higher

So Bølgerne er højere i dag means The waves are higher today.

Even if English might sometimes say the waves are high today, Danish here uses the comparative, suggesting they are higher than usual, higher than before, or higher than on another day.

I dag means today.

It is a time expression, and here it tells us when the waves are higher:

• Bølgerne er højere i dag = The waves are higher today

Danish uses i dag very much like English uses today.

Here så means so, therefore, or as a result.

It connects the two ideas:

• The waves are higher today
• so we are not sailing out

So så shows consequence.

Because in a normal Danish main clause, the negative word ikke usually comes after the finite verb.

Here:

• vi = subject
• sejler = finite verb
• ikke = not
• ud = out

So the normal order is:

• vi sejler ikke ud

This is a very important Danish pattern. English speakers often want to put ikke before the verb, but in main clauses that is usually wrong.

Sejler ud literally means sail out, but in context it often means:

• go out by boat
• head out onto the water
• sail away from shore

So vi sejler ikke ud means they are not going out on the water.

The ud adds the idea of outward movement.

Yes, that is a helpful way to think about it.

In sejler ud, ud functions a lot like out in English:

• gå ud = go out
• køre ud = drive out
• sejle ud = sail out

Danish often uses these small direction words with verbs, and they can change or sharpen the meaning of the verb.

Because så here is a coordinating conjunction, not a fronted adverb.

That means the second clause starts normally:

• så vi sejler ikke ud

with standard word order:

• conjunction
• subject
• verb
• ikke
• particle

If something else were placed first inside the clause itself, then Danish might show inversion. But after coordinating så, the clause simply begins normally.

You could also say:

• I dag er bølgerne højere, så vi sejler ikke ud.

Here I dag is moved to the front. In that case Danish uses verb-second order, so er comes before bølgerne:

• I dag er bølgerne højere

That is a very common Danish word-order pattern.

Roughly, it sounds something like BUHL-yer-neh, but that is only an approximation.

A few important points:

• ø is a vowel that English does not really have
• the g in bølge is soft
• the ending -rne can sound reduced in natural speech

If you want a better target:

• bølge is roughly BUHL-ye
• bølgerne is roughly BUHL-yer-neh

The exact sound is best learned by listening to native audio, especially because Danish pronunciation is often less phonetic than its spelling suggests.

In this sentence, vi sejler ikke ud is the normal and correct order.

The sequence is:

• subject: vi
• verb: sejler
• negation: ikke
• particle/adverb: ud

So ikke normally comes before ud here. That order is not mainly about emphasis; it is the standard Danish structure.

Yes, it sounds very natural.

It is a simple, everyday way to explain a decision based on conditions:

• Bølgerne er højere i dag = the situation
• så vi sejler ikke ud = the consequence

A Dane could easily say this in conversation about weather, boating, or sea conditions.