Learn French: L'eau est là. - The water is there.

Eau is a feminine noun. When a word starts with a vowel, both le and la shrink to l' so the words flow together. But if you wanted to say 'a water', you would use the feminine indefinite article: une eau.

How do you pronounce eau?

It sounds exactly like the English letter 'O'. In French, the letters eau together always make this simple 'oh' sound.

Why does là have an accent mark on the 'a'?

The accent tells you this is the word for 'there'. Without the accent, la is the word for 'the' used with feminine nouns. The accent doesn't change the pronunciation at all, it just helps you tell the two words apart in writing.

Do I pronounce the 's' and 't' at the end of est?

No, both the 's' and 't' are silent. Est (which means 'is') just sounds like a short English 'eh'. It is the form of the verb être (to be) used for 'he', 'she', or a thing like water.