I sommar vill jag bada i havet varje dag.

I sommar is a time expression meaning this summer or during the summer. Swedish often puts time expressions first to set the scene.

Starting with I sommar gives the sentence a natural topic-first feel: first the time, then what the speaker wants.

You could also say:

• Jag vill bada i havet varje dag i sommar.

That is also correct, but it places slightly more focus on jag vill bada first, while I sommar at the front highlights the time period.

This is because Swedish main clauses usually follow the V2 rule: the finite verb must come in the second position.

In this sentence:

• I sommar = first position
• vill = second position
• jag = comes after the verb

So:

• I sommar vill jag bada ... = correct
• I sommar jag vill bada ... = incorrect

This is a very important Swedish word-order pattern.

Compare:

• Jag vill bada i havet varje dag.
• I sommar vill jag bada i havet varje dag.

Both are correct, but when something other than the subject comes first, the verb still has to stay second.

In the expression i sommar, Swedish uses the bare noun without the definite ending.

This is common in fixed time expressions:

• i dag = today
• i morgon = tomorrow
• i år = this year
• i sommar = this summer

So i sommar does not literally work like in the summer with an article. It functions more like this summer.

By contrast, på sommaren usually means in summer / during the summer season in general, not specifically this summer.

Because Swedish infinitives after modal verbs do not use att.

Here:

• vill = want
• bada = bathe/swim/go swimming

So:

• vill bada = want to swim

This is like English modal-style constructions, even though want is not a modal in English.

Compare:

• Jag vill bada. = I want to swim.
• Jag kan bada. = I can swim / I am able to swim.
• Jag måste bada. = I must swim.

But in other cases Swedish often does use att before an infinitive, depending on the verb.

Not exactly.

Bada often means to bathe, to go for a swim, or to be in the water for pleasure. It is the natural word when talking about swimming at the beach, in a lake, or in the sea as an activity.

Simma means to swim in the sense of the physical action or skill.

So:

• Jag vill bada i havet. = I want to go swimming / bathe in the sea.
• Jag vill simma i havet. = I want to swim in the sea.

In many contexts both can work, but bada sounds more natural for casual summer swimming.

Because the person wants to be in the water, not on the sea.

• i havet = in the sea
• på havet = on the sea

So:

• bada i havet = bathe/swim in the sea
• vara på havet = be out on the sea, for example in a boat

Since bada involves entering the water, i is the natural preposition.

Havet is the definite form of hav:

• ett hav = a sea / an ocean
• havet = the sea

In Swedish, it is very natural to say i havet when referring to the sea as the body of water you would swim in.

Using the definite form here is idiomatic, similar to how English often says the sea rather than just sea.

Usually hav(et) is best understood as sea, but depending on context it can also refer to a larger body of salt water and may sometimes be translated as ocean.

In a sentence like this, i havet most naturally means in the sea.

If the learner is thinking of the difference from lake, that would be:

• hav = sea
• sjö = lake

So bada i havet suggests salt water, beach, coast, summer swimming, and so on.

Varje dag is the standard way to say every day.

• varje = every
• dag = day

So:

• varje dag = every day

Alla dagar literally means all days, but that is much less natural in this context.

For repeated frequency, Swedish normally uses:

• varje dag = every day
• varje vecka = every week
• varje sommar = every summer

Yes, it can be moved, but the emphasis changes a little.

The original sentence:

• I sommar vill jag bada i havet varje dag.

This sounds very natural. The idea builds toward the frequency: every day.

You could also say:

• I sommar vill jag varje dag bada i havet.

This is grammatically possible, but less natural in everyday speech.

Or:

• Jag vill bada i havet varje dag i sommar.

Also correct, with a different flow.

So the original word order is a very idiomatic choice.

A useful breakdown is:

• I sommar = time expression
• vill = finite verb
• jag = subject
• bada = infinitive
• i havet = prepositional phrase
• varje dag = adverbial of frequency

So the pattern is:

Time + finite verb + subject + infinitive + place + frequency

That makes this sentence a good example of two important Swedish features at once:

1. V2 word order in main clauses
2. modal verb + infinitive without att