But inthe examples, “She is a good swimmer” “It is a pretty dress” &”That is the dress I wear to work” all seem specific why use C’est?

Hi Susan,

If you scroll down the Q&A section at the bottom of this lesson , you will see that there is quite a lot of discourse regarding when to use, c'est and il/elle est-

You cannot say in French - 'Elle est une bonne nageuse' but, 'C'est une bonne nageuse' is the only correct sentence.

It is the same for "It is a pretty dress" you cannot use  Elle here -

"C'est une jolie robe " is the only acceptable answer.

Hope this helps!

Hi Paola,

You can also say :

Elle est bonne nageuse ( no 'une' which is never possible after - elle est ....

This is why we say :

Elle est prof d'anglais

Il est architecte

elles sont médecins 

etc...