Ons sal een ding nodig hê, naamlik water.

Because een means one in the numerical sense, while 'n is the indefinite article, like a / an in English.

So:

• 'n ding = a thing
• een ding = one thing

In this sentence, the speaker is emphasizing that only one thing is needed, so een is the correct choice.

Sal is used to form the future, similar to will in English.

So:

• Ons sal ... hê = We will have / will need ...
• Ons sal een ding nodig hê = We will need one thing

Afrikaans often uses sal where English uses will.

This happens because of Afrikaans word order with auxiliaries and verb phrases.

The expression nodig hê means to need. When you use a finite auxiliary like sal, the main verb goes to the end:

• Ons het water nodig. = We need water.
• Ons sal water nodig hê. = We will need water.

So hê moves to the end because sal is already taking the main verb position earlier in the clause.

Learners often think about it both ways, and that is understandable.

In practice, nodig hê functions as the usual Afrikaans way to say need. Literally, nodig means something like necessary / needed, and hê means have, but together they form the normal expression for needing something.

For example:

• Ek het hulp nodig. = I need help.
• Jy sal tyd nodig hê. = You will need time.

So even though the parts are separate, you should learn nodig hê as a set expression meaning to need.

Naamlik means namely, that is, or specifically.

It introduces a more exact identification of what was just mentioned:

• een ding → one thing
• naamlik water → namely water

So it narrows down the general phrase one thing to the specific item water.

Yes, it is normal and helpful here.

Naamlik introduces an explanation or specification, so it is commonly set off with a comma:

• Ons sal een ding nodig hê, naamlik water.

This is similar to English punctuation in sentences like:

• We need one thing, namely water.

Because water is being used as an uncountable noun, just like in English.

Compare:

• Ons het water nodig. = We need water.
• Ons het 'n bottel water nodig. = We need a bottle of water.

You normally do not use 'n before a mass noun like water unless you mean a unit or a type.

The accent in hê is part of the normal spelling. It helps distinguish this word and marks its vowel.

Hê means have.

Examples:

• Ek het 'n boek. = I have a book.
• Ons sal dit nodig hê. = We will need it.

So in this sentence, hê is the infinitive form of have, used as part of nodig hê.

Yes, but the meaning changes in time.

• Ons het een ding nodig. = We need one thing. / We have one thing we need.
• Ons sal een ding nodig hê. = We will need one thing.

The first is present-time need; the second is future-time need.

Yes, ons is the normal subject pronoun for we.

Examples:

• Ons gaan. = We are going.
• Ons sal wag. = We will wait.

So in this sentence, ons simply means we.

The given sentence is correct and clear, especially in slightly formal or careful language.

In everyday speech, people might also say things like:

• Ons gaan net water nodig hê.
• Ons het net een ding nodig: water.

The original version with naamlik sounds a bit more formal or explanatory, similar to English namely.

The g in Afrikaans is usually not pronounced like the English g in go. It is typically a throaty sound, similar to the ch in Scottish loch or German Bach.

Very roughly:

• nodig ends with that throatier g
• naamlik has the same kind of sound
• ding ends in ng, which is more like English sing

So:

• ding ≈ English ding with normal ng
• nodig ≈ NOH-dukh / NOH-dikh depending on accent
• naamlik ≈ NAAM-likh

The exact sound varies by speaker, but it is usually much harsher than English g.