Se vuoi tuffarti dal trampolino, fallo solo quando la corsia è libera.

Se means if, and vuoi means you want.

So Se vuoi... literally means If you want to...

In this sentence, it introduces a condition in a very natural way:

• Se vuoi tuffarti dal trampolino... = If you want to dive from the diving board...

It sounds like a normal instruction, not especially formal or literary.

Because the verb is tuffarsi, not just tuffare, when it means to dive in or to plunge.

• tuffare = to dip/submerge something
• tuffarsi = to dive, to plunge oneself

The ending -ti means yourself:

• tuffarsi = to dive oneself
• tuffarti = to dive yourself / to dive in

After a verb like vuoi, Italian often uses the infinitive with the pronoun attached:

• vuoi tuffarti = you want to dive

This is very common:

• voglio alzarmi = I want to get up
• puoi sederti = you can sit down

Dal is a contraction of da + il:

• da = from
• il = the
• dal = from the

So:

• dal trampolino = from the diving board

A useful warning for English speakers: trampolino here means diving board, not trampoline.

Fallo means do it.

It comes from:

• fa' = do! (the tu imperative of fare)
• lo = it

Together:

• fa' + lo → fallo

Here lo refers to the action of diving from the board:

• If you want to dive from the board, do it only when the lane is free.

In Italian, with an affirmative command, object pronouns are usually attached to the end of the verb.

So:

• fai = you do
• fa'! = do!
• fallo! = do it!

This is normal with imperatives:

• dimmi = tell me
• portalo = bring it
• scrivilo = write it

So fallo is not a special word by itself; it is a command form plus a pronoun.

Because when certain short imperative forms take an attached pronoun, the first consonant of the pronoun often doubles.

So:

• fa' + lo → fallo
• di' + lo → dillo
• da' + mi → dammi
• va' + ci → vacci

This is just a standard spelling pattern you need to learn with these imperative forms.

In this context, corsia means lane, specifically a swimming lane in a pool.

So:

• la corsia è libera = the lane is free / clear

Outside swimming, corsia can also mean a road lane or a corridor-like passage, depending on context. But here it clearly refers to the pool lane.

Because corsia is a feminine singular noun.

In Italian, adjectives agree with the noun they describe:

• la corsia = feminine singular
• libera = feminine singular form of free

Compare:

• il posto è libero = the spot is free
• la corsia è libera = the lane is free

Quando means when, so solo quando la corsia è libera means only when the lane is free.

This emphasizes the moment or circumstance in which the action is allowed.

You could also say:

• fallo solo se la corsia è libera = do it only if the lane is free

That would also be correct and natural. The difference is small:

• solo quando = only when
• solo se = only if

In this sentence, quando sounds very natural because it gives a practical safety instruction.

Not perfectly, because Italian and English package actions a bit differently.

A very literal version would be:

• If you want to dive yourself from the diving board, do it only when the lane is free.

But that sounds unnatural in English.

A natural English version is:

• If you want to dive from the diving board, do it only when the lane is clear.

So the Italian is not strange; it just uses a reflexive form (tuffarsi) where English normally does not.

You would change the verb forms:

• Se volete tuffarvi dal trampolino, fatelo solo quando la corsia è libera.

Changes:

• vuoi → volete = you all want
• tuffarti → tuffarvi = to dive yourselves
• fallo → fatelo = do it

So the structure stays the same, but the verbs agree with you all.

For formal singular Lei, you would normally say:

• Se vuole tuffarsi dal trampolino, lo faccia solo quando la corsia è libera.

Notice the changes:

• vuoi → vuole
• tuffarti → tuffarsi
• fallo → lo faccia

The command becomes more formal and uses the formal imperative/subjunctive-style form faccia.