Die Kinder tun so, als hätten sie die Badewanne noch nie gesehen, und lachen über das viele Wasser.

It means to pretend / to act as if ...

So:

• so tun = to act like that / to behave in a certain way
• so tun, als ... = to act as if ...

In this sentence, Die Kinder tun so, als ... means the children are pretending.

A very common pattern is:

• so tun, als ob ...
• or the shorter/literary version used here: so tun, als ...

Examples:

• Er tut so, als ob er krank wäre. = He acts as if he were sick.
• Sie tut so, als wüsste sie nichts. = She pretends she knows nothing.

Because German uses the subjunctive here, specifically Konjunktiv II, to show that this is not real, only something that seems true or is being pretended.

The children are not actually people who have never seen a bathtub. They are only acting that way. So German marks that unreality with hätten.

Compare:

• sie haben die Badewanne nie gesehen = they have never seen the bathtub
  (presented as a real fact)
• als hätten sie die Badewanne nie gesehen = as if they had never seen the bathtub
  (not a real fact; only appearance/pretending)

So hätten is the correct form because the sentence is about an unreal comparison.

Both are possible.

German has two common ways to say as if:

• als ob sie die Badewanne noch nie gesehen hätten
• als hätten sie die Badewanne noch nie gesehen

They mean the same thing.

The version with als + verb first is a shorter alternative to als ob. It is very common in written German and perfectly normal in speech too.

So this sentence could also be written as:

• Die Kinder tun so, als ob sie die Badewanne noch nie gesehen hätten, und lachen über das viele Wasser.

Same meaning, just a different structure.

Because German puts the verb parts into a verb bracket.

The full verbal idea is hätten gesehen = had seen.

In the clause als hätten sie die Badewanne noch nie gesehen:

• hätten comes near the front
• gesehen goes to the end

That is normal for German clauses with multiple verb parts.

Compare:

• Sie haben die Badewanne gesehen.
• ..., als hätten sie die Badewanne gesehen.

In the second version, the participle gesehen stays at the end of the clause.

Noch nie means never before or not ever up to now.

It is a very common expression:

• Ich war noch nie in Berlin. = I have never been to Berlin.
• Hast du das noch nie gesehen? = Have you never seen that before?

In this sentence:

• als hätten sie die Badewanne noch nie gesehen

it means as if they had never seen a bathtub before.

The word noch adds the sense of up to this point.

Because German uses articles more often than English does.

In English, we might say they had never seen a bathtub or the bathtub, depending on context. German often prefers a definite article when the thing is understood from the situation or treated as a familiar object in the scene.

So die Badewanne here is natural German.

It does not necessarily mean one very specific famous bathtub. It can simply refer to the bathtub in this situation.

The verb is lachen über + accusative, which means:

• to laugh at
• to laugh about

So:

• über das viele Wasser lachen = to laugh at/about all the water

This is just the normal preposition used with lachen when something is the object of the laughter.

Examples:

• Sie lachen über den Witz. = They laugh at the joke.
• Er lacht über sich selbst. = He laughs at himself.

So über is not random here; it belongs to the verb pattern.

Both are possible, but they feel slightly different.

• viel Wasser = a lot of water
• das viele Wasser = all that water / the large amount of water

With das viele Wasser, the speaker points more clearly to the water as something noticeable in the situation.

So here it sounds a bit like:

• they laugh at all that water

It makes the water feel more concrete and visually present.

Also, the adjective ending -e in viele is there because it comes after the definite article das.

The comma is not really there because of und. It is there because the als clause has just ended.

Structure:

• main clause: Die Kinder tun so
• inserted comparison clause: als hätten sie die Badewanne noch nie gesehen
• continuation: und lachen über das viele Wasser

So the comma marks the end of the als clause:

• ..., als hätten sie ... gesehen, und lachen ...

Without that inserted clause, there would normally be no comma:

• Die Kinder lachen und spielen.

Because the subject stays the same.

German often leaves out a repeated subject in coordinated structures when it is already clear:

• Die Kinder tun so ..., und lachen ...

This means:

• The children pretend ..., and (they) laugh ...

German could repeat the subject, but it is usually unnecessary here.

No, not in this expression.

So tun is a fixed idiom meaning to act / to pretend.

So:

• so tun, als ... = to pretend / to act as if ...

But machen does not work in this idiomatic way.

So you say:

• Er tut so, als wäre er müde.

not:

• Er macht so, als wäre er müde. ✗

It is Konjunktiv II Perfekt.

Breakdown:

• hätten = subjunctive form of haben
• gesehen = past participle of sehen

This form is used because the sentence refers to something that would have happened before the children’s current behavior.

They are acting now as if they had never seen the bathtub before.

So the structure matches English quite closely:

• as if they had never seen ...

It is both:

1. unreal → so German uses Konjunktiv II
2. earlier than the pretending/laughing → so German uses the perfect form

Not naturally in this case.

With as if clauses, German usually prefers a direct Konjunktiv II form like:

• als hätten sie ... gesehen
• als ob sie ... gesehen hätten

Using würden is possible with some verbs when there is no simple clear subjunctive form, but here hätten is the standard and best choice.

So:

• als hätten sie ... gesehen ✔
• als ob sie ... gesehen hätten ✔
• als würden sie ... gesehen haben ✗ awkward / unnatural here

So learners should treat als hätten sie ... as the normal pattern.