chulbalhagi jeone mulbyeongeul kkok gajyeowa.

Both are possible, but they are built a little differently.

• 출발 전에 = before departure / before leaving
  • Here, 출발 is being treated more like a noun.
• 출발하기 전에 = before departing / before you leave
  • Here, 출발하다 is turned into a noun-like phrase with -기.

So:

• 출발 전에 sounds a bit more compact and noun-like.
• 출발하기 전에 makes the action of leaving feel more explicit.

In everyday Korean, both are natural.

-기 전에 means before doing something.

Structure:

• verb stem + -기 전에

Examples:

• 먹기 전에 = before eating
• 자기 전에 = before sleeping
• 출발하기 전에 = before leaving

So in this sentence, 출발하기 전에 sets up the time: before leaving.

Because -기 turns a verb into a noun-like form.

• dictionary form: 출발하다 = to depart
• verb stem: 출발하-
• • 기 → 출발하기

This lets the verb act like a thing/event, so it can be used with expressions like:

• -기 전에 = before doing
• -기 시작하다 = start doing
• -기 싫다 = dislike doing

So 출발하기 전에 literally has the sense of before the act of departing.

물병 means water bottle, and -을 is the object particle.

So:

• 물병 = water bottle
• 물병을 = the water bottle / a water bottle (as the object of the verb)

It marks what is being brought.

In this sentence:

• 물병을 꼭 가져와 = bring the water bottle for sure / make sure to bring a water bottle

꼭 means something like:

• definitely
• certainly
• be sure to
• without fail

It adds emphasis. The speaker is not just saying bring a water bottle, but make sure you bring it.

Compare:

• 물병을 가져와. = Bring a water bottle.
• 물병을 꼭 가져와. = Be sure to bring a water bottle.

So 꼭 makes the instruction stronger and more important.

가져오다 means to bring.

It is made from:

• 가지다 = to have / hold
• 오다 = to come

Over time, this combination became the common verb 가져오다 = bring (toward the speaker / to here).

Its informal command form is:

• 가져와 = bring it

So:

• 물병을 가져와 = bring the water bottle

Using just 가져 would not mean the same thing here.

This is an important distinction.

• 가져오다 → 가져와 = bring (toward the speaker / to the destination being focused on)
• 가져가다 → 가져가 = take (away from the speaker / from here to somewhere else)

So the choice depends on perspective.

Examples:

• If you are at home and I say 학교에 올 때 물병을 가져와, I mean bring it with you (to where I am / to the relevant place).
• If I hand you a bottle and say 이거 가져가, I mean take this with you.

In your sentence, 가져와 is being used in the common sense of bring it along.

가져와 is a casual imperative form.

It is:

• natural between close friends
• natural from a parent to a child
• natural when speaking to someone younger
• too casual for formal situations

Depending on tone and relationship, it can sound:

• friendly
• direct
• bossy

More polite versions would be:

• 출발하기 전에 물병을 꼭 가져와요.
• 출발하기 전에 물병을 꼭 가져오세요.

So 가져와 is not automatically rude, but it is definitely informal.

Korean very often leaves out the subject when it is obvious from context.

So this sentence does not explicitly say:

• you
• we
• he/she

But from the command form 가져와, we know the speaker is telling someone to do it, usually you.

In English, we must say the subject less often in commands too:

• Bring the water bottle.

So the missing subject in Korean is very natural here.

It can mean either, depending on context.

Korean usually does not mark a/the the way English does.

So 물병을 꼭 가져와 could mean:

• Bring the water bottle if both people know which one
• Bring a water bottle if it is nonspecific

You determine that from the situation, not from the noun itself.

Not exactly the same.

• 물병을 가져와 = bring a water bottle
• 물을 가져와 = bring water

The first focuses on the container. The second focuses on the substance.

If the idea is bring your bottle with water in it, Korean often still uses 물병 because that is the practical item being carried.

These expressions are related but not interchangeable.

• 출발하기 전에 = before leaving
• 출발할 때 = when leaving / at the time of leaving
• 출발하면 = if/when you leave

Examples:

• 출발하기 전에 물병을 꼭 가져와.
  • Be sure to bring a water bottle before you leave.
• 출발할 때 물병을 가져와.
  • Bring a water bottle when you leave.
• 출발하면 연락해.
  • When/if you leave, contact me.

So -기 전에 specifically emphasizes that the action must happen earlier than the departure.

Yes, depending on context.

Because 가져오다 literally has the sense of bring toward here, the sentence can be understood as:

• Bring the water bottle here or
• Bring the water bottle with you

In real-life Korean, context decides which one is intended. If the speaker is talking about a trip or leaving for somewhere, English often translates it naturally as bring it with you.

You could say:

• 출발하기 전에 물병을 꼭 가져와요.
• 출발하기 전에 물병을 꼭 가져오세요.

Nuance:

• 가져와요 = polite but still conversational
• 가져오세요 = more standard polite request/command

If you want to sound even softer:

• 출발하기 전에 물병을 꼭 가져와 주세요.
• 출발하기 전에 물병을 꼭 가져와 줘요. (less formal)

So the original sentence is casual, and these are more polite alternatives.