المي بحارة السباحة هاي عميقة.

Because Levantine Arabic usually leaves out the present-tense to be in sentences like this.

So instead of saying The water in this swimming lane is deep, Arabic literally says something closer to:

the-water in this swimming lane deep

This is called a nominal sentence.
If you wanted past or future, then you would normally add something like كان or another verb.

المي is the Levantine dialect word for the water.

A learner who knows Modern Standard Arabic may expect الماء, but in everyday Levantine, مي is much more common than ماء.

So:

• مي = water
• المي = the water

This is a very normal dialect feature.

Here it is best understood as:

• بـ = in
• حارة = lane

So بحارة is really بـ + حارة, written together because short prepositions like بـ attach directly to the following word in Arabic spelling.

So the phrase means in a lane or here more specifically in the swimming lane.

It means the swimming lane.

Literally, it is something like:

• حارة = lane
• السباحة = swimming

Together, حارة السباحة means swimming lane.

This kind of noun-plus-noun structure is very common in Arabic. English often uses the same idea too, as in swimming pool, school bus, or coffee cup.

In Levantine Arabic, demonstratives like this often come after the noun.

So:

• حارة السباحة هاي = this swimming lane

That is very natural in Levantine.

English says this lane, but Levantine often says something more like the lane this.

You may also hear pre-noun demonstratives in some contexts, but the post-noun pattern is extremely common in spoken Levantine.

هاي refers to حارة السباحة, not to المي.

So the structure is:

• المي = the water
• بحارة السباحة هاي = in this swimming lane
• عميقة = deep

So هاي is describing the lane, not the water.

If it were referring to the water, you would expect a different structure, such as المي هاي for this water.

Because حارة is a feminine noun, and هاي is the feminine form of this.

So:

• masculine: often هاد / هيدا depending on the variety
• feminine: هاي

Since حارة is feminine, هاي is the correct form here.

Because it agrees with المي.

In Levantine, مي is commonly treated as feminine, so the adjective also appears in the feminine form:

• عميقة = deep (feminine)

That is why you do not see عميق here.

So even though هاي is next to حارة, the adjective عميقة is describing المي.

Because in Arabic, expressions like swimming lane often use a noun phrase where the second noun is definite with الـ.

So حارة السباحة is a normal Arabic way to say swimming lane.

This is similar to other set expressions such as:

• حوض السباحة = swimming pool
• غرفة النوم = bedroom

So the الـ here is not strange; it is part of a very common pattern.

Yes, it is normal.

The sentence is organized like this:

• المي = the subject
• بحارة السباحة هاي = a prepositional phrase giving location
• عميقة = the predicate adjective

So literally it is something like:

The water, in this swimming lane, deep.

English usually needs is and often prefers a slightly different rhythm, but the Arabic order is perfectly natural.

Yes, in plain Arabic spelling, بحارة can also be read as sailors in other contexts.

But here, the sentence structure makes it clear that it is بـ + حارة = in a lane.

Context is what tells you which meaning is intended. That kind of ambiguity is normal in Arabic writing because short vowels are usually not written.

A very literal breakdown would be:

• المي = the water
• بحارة السباحة هاي = in this swimming lane
• عميقة = deep

So the whole sentence is roughly:

The water in this swimming lane is deep.

That is the natural way to understand it, even though the Arabic grammar is built differently from English.