Kad idemo na izlet, uvijek nosimo vodu sa sobom.

Yes. Kad means when here.

In this sentence, Kad idemo na izlet means When we go on a trip / When we are going on an outing.

A learner should know that Croatian also has kada, which usually means the same thing.

• kad = more common in everyday speech
• kada = a bit fuller or sometimes slightly more formal

So you could also say:

• Kada idemo na izlet, uvijek nosimo vodu sa sobom.

Both are natural.

Idemo is the 1st person plural present tense of ići (to go).

So:

• idem = I go
• ideš = you go
• ide = he/she/it goes
• idemo = we go
• idete = you go (plural/formal)
• idu = they go

Here, idemo means we go.

In sentences like this, the present tense is often used for habitual actions, so Kad idemo na izlet means something like:

• Whenever we go on a trip
• When we go on outings

not just one specific trip.

Croatian uses different prepositions depending on the kind of movement or idea involved.

With izlet (trip / outing / excursion), the normal expression is:

• ići na izlet = to go on a trip / go on an outing

So na + accusative is the fixed and natural pattern here.

That is why you get:

• na izlet

and not u izlet.

This is similar to how languages often use different prepositions idiomatically. English says go on a trip, not go to a trip in the same sense.

It is in a case here: it is in the accusative singular.
The reason it looks unchanged is that izlet is a masculine inanimate noun, and for many masculine inanimate nouns, the accusative singular has the same form as the nominative singular.

So:

• nominative: izlet
• accusative: izlet

Even though the form looks the same, the case is still accusative because na with movement usually requires accusative.

Uvijek means always.

Here it modifies the main clause:

• uvijek nosimo vodu sa sobom = we always carry water with us

Its placement is very natural. Croatian word order is fairly flexible, but uvijek often appears before the verb or near the part it emphasizes.

So these are all possible, though some sound more neutral than others:

• Kad idemo na izlet, uvijek nosimo vodu sa sobom. ← very natural
• Kad idemo na izlet, vodu uvijek nosimo sa sobom.
• Uvijek nosimo vodu sa sobom kad idemo na izlet.

The original version is a very standard way to say it.

Because voda is the direct object of the verb nosimo (we carry), so it must be in the accusative case.

• nominative: voda = water
• accusative: vodu

So:

• nosimo vodu = we carry water

This is a very common pattern in Croatian:

• imam knjigu = I have a book
• vidim kuću = I see a house
• nosimo vodu = we carry water

Yes, nosimo literally means we carry / we bring / we take along, depending on context.

The verb is nositi. In this sentence, it means something like:

• we carry water with us
• we bring water along
• we take water with us

English may choose different verbs, but Croatian naturally uses nositi here.

Sa sobom means with oneself / with ourselves / with you / with him/her, depending on the subject.

The key word is sobom, which comes from the reflexive pronoun sebe.
This reflexive pronoun refers back to the subject of the sentence.

So in:

• nosimo vodu sa sobom

the subject is we, so sa sobom means:

• with ourselves
• more naturally in English: with us

This is why Croatian uses sobom instead of a regular pronoun like nama here.

Because Croatian normally uses the reflexive form when the phrase refers back to the subject itself.

Here the subject is we, and the meaning is we carry water with us. Since us refers to the same people as the subject we, Croatian prefers:

• sa sobom

rather than:

• s nama

Using s nama would usually sound less natural in this kind of sentence, because it is not reflexive.

A useful comparison:

• Nosimo vodu sa sobom. = We carry water with us.
• On nosi vodu sa sobom. = He carries water with him.
• Oni nose vodu sa sobom. = They carry water with them.

The reflexive form stays the same even though the subject changes.

Both s and sa mean with, but sa is often used for easier pronunciation before certain consonant combinations.

Because sobom starts with s, Croatian normally says:

• sa sobom

not:

• s sobom

So this is mainly a pronunciation and euphony issue.

You will often see:

• s prijateljem = with a friend
• sa mnom = with me
• sa sobom = with oneself / with us, etc.

Because Kad idemo na izlet is a subordinate clause at the beginning of the sentence.

Croatian usually separates this kind of introductory clause from the main clause with a comma:

• Kad idemo na izlet, uvijek nosimo vodu sa sobom.

This is similar to English:

• When we go on a trip, we always take water with us.

So the comma marks the boundary between:

1. the when-clause
2. the main statement

Most naturally, it describes a general habit.

• Kad idemo na izlet = When we go on trips / Whenever we go on an outing
• uvijek nosimo vodu sa sobom = we always bring water with us

So the whole sentence means something habitual or repeated.

If you wanted to talk about one specific future occasion, context would usually make that clear, but without extra context this sentence sounds like a general rule or habit.

Yes. Croatian word order is more flexible than English word order.

The original sentence is very natural:

• Kad idemo na izlet, uvijek nosimo vodu sa sobom.

But you could also hear:

• Uvijek nosimo vodu sa sobom kad idemo na izlet.
• Kad idemo na izlet, vodu uvijek nosimo sa sobom.

The meaning stays basically the same, but the emphasis can shift slightly.

For learners, the original version is a good neutral pattern to remember:

• time clause first
• then adverb uvijek
• then verb + object + sa sobom