Kelly Packard -- Good Genes or Good Docs?

Kelly Packard's beauty is running in slow motion!

Here's a 22-year-old version of the "Baywatch" lifesaver in a promo pic back in 1997 (left) and 20 years later ... the 42-year-old mother of four at a movie marathon in Los Angeles last month (right).

"Forever and always, I'm always here!"

The question is...