Sie kann gut tauchen.

In this sentence, Sie can only mean she.

The key is the verb form kann:

• sie kann = she can
• sie können = they can
• Sie können = you can (formal)

Because the sentence uses kann and not können, the subject must be singular feminine: she.

This happens because können is a modal verb.

In German main clauses, a modal verb is usually:

• conjugated in the second position
• while the other verb stays in the infinitive at the end

So:

• Sie = subject
• kann = conjugated modal verb
• gut tauchen = the rest, with tauchen at the end

This is a very common German pattern:

• Ich kann schwimmen.
• Er will kommen.
• Wir müssen gehen.

German main clauses usually follow the V2 rule, which means the finite verb goes in the second position.

Here:

• 1st position: Sie
• 2nd position: kann

The infinitive tauchen is not the finite verb, so it goes to the end.

Because it is the main verb in the infinitive, and it depends on the modal verb kann.

With modal verbs like können, müssen, wollen, sollen, dürfen, mögen, the second verb usually goes to the end in a main clause:

• Sie kann gut tauchen.
• Ich muss heute arbeiten.
• Wir wollen morgen fahren.

So this word order is completely normal.

Because gut is being used as an adverb, not as an adjective before a noun.

Here it describes how she can dive:

• gut tauchen = to dive well

Adverbs in German do not take adjective endings.

Compare:

• Sie ist gut. = Here gut is an adjective after sein
• Sie kann gut tauchen. = Here gut is an adverb modifying the verb

In German, adverbs like gut often come before the infinitive they modify.

So:

• gut tauchen = to dive well

This placement is very natural in German, especially when the infinitive is at the end because of a modal verb.

Yes, you can.

• Sie taucht gut. = She dives well
• Sie kann gut tauchen. = She can dive well

The second version includes the idea of ability or capability because of kann.

So the sentences are similar, but not identical:

• Sie taucht gut focuses on what she does well
• Sie kann gut tauchen focuses more on her ability

No. After a modal verb like können, German uses the bare infinitive.

So you say:

• Sie kann gut tauchen.

Not:

• Sie kann gut zu tauchen.

Modal verbs are one of the most important cases where German does not use zu.

Tauchen usually means to dive.

Depending on context, it can mean:

• to dive underwater
• to go diving
• sometimes specifically scuba diving

If the sentence appears by itself, to dive is the safest basic meaning.

The most natural negative version is:

• Sie kann nicht gut tauchen.

This means she cannot dive well or is not good at diving.

Here nicht usually comes before the part being negated, and in this sentence it naturally goes before gut:

• nicht gut tauchen = not dive well

The infinitive is können.

Here are some present-tense forms:

• ich kann
• du kannst
• er/sie/es kann
• wir können
• ihr könnt
• sie/Sie können

So kann is the 3rd person singular form of können.

At the beginning of the sentence, capitalization does not help you distinguish the meaning, because the first word is capitalized anyway.

But the verb form does help:

• Sie kann = she can
• Sie können = you can (formal)

So in this sentence, the verb makes the meaning clear.

Tauchen is pronounced roughly like TOW-khen.

A few helpful points:

• au sounds like the ow in cow
• ch here is the softer German ch sound
• -en at the end is usually light, not strongly stressed

The stress is on the first syllable: TAU-chen.