After a breast implant, when is it safe to go swiming?

Soon: You should be able to swin very soon after this surgery. The skin incisions seal within 24 hours.

Depends on closure: The incision should be watertight in 24 hours. I will let my patients shower at that time, but restrict submerging the wound until one week if it is healing normally. Open wounds should not be submerged. Good results are the product of team work. Every plastic surgeon has a slightly different protocol, be a good team mate and ask you plastic surgeon before you go swimming. ;).

Complete wound seal: That is durable enough to be submerged in bacteria-filled water is what is needed, and this is "dicey" at one week. I recommend waiting 3 weeks (normal healing, longer if any healing issues) before bathtub, swimming pools, jacuzzis, hot tubs, oceans, lakes, streams (you get the idea). Showering is ok right away as I use an adherent tegaderm (clear bandage) so can see the properly-healing wound.

When your surgeon: Gives you the ok, you can go. I usually say 4 weeks.