Is it safe to swim with strep throat?

Yes. All things considered, if you feel well enough to swim, there is o negative impact for doing so with this minor issue.
Yes, conditionally. Swimming with strep. Throat is acceptable if you have no fever, minimal fatigue, are well-hydrated and have been treated with antibiotics for at least 24 hours. The first three reasons are for your safety, the last one primarily for the safety of others, as you are unlikely to be contagious after 24 hours of antibiotic therapy.