Zwemdiploma. A must or nice to have?

Hi all.

Our son has a zwemdiploma but only ever had to use it once (summer camp). Nobody ever asked for it apart from that and now he's a teenager.

Our daughter is now taking lessons too but she has a bit of a learning disability and she is far behind the rest of the group. We're currently thinking of letting her stay until the contract is up, but after that handling it ourselves. We have water just behind the house and can practice daily during the summer months. It's important to us that she knows how to swim well. The downside is of course that we will not get a diploma.

I'm wondering if it's worth continuing this as we'll pay at least twice the "regular" amount to get her to learn, maybe even more if she struggles, only to get a worthless diploma.

What is your take on this?

(like I said, she will know how to swim regardless so no flaming please)