Can you swim with my Apple Watch Series 7?

My granddaughter has been a competitive swimmer for years, and always wears her Apple Watch....so, yes, it's fine.

You should, however, use it properly when swimming: How to use Water Lock and eject water from your Apple Watch - Apple Support

Hope this helps.

Yes. You can absolutely swim with your Series 7. Deep water is not advised, but pool swimming is perfectly fine. I’ve been doing it since day 1 and have had no issues