Public pools or Beach?

I'm traveling to Naples in a couple days and my family really want to get into water while there but I'm not sure what's the best/easier. We're only there a couple days so I don't want to it to be to hard to get to.

I've seen that Gaiola is good but it's well over an hour to get there on public transportation. I don't think spending that much time traveling is a good idea.

I found Jemming SRL but there's no guarantee we'll get in.

Some additional details: we're staying off the Dante metro station and my wife and youngest daughter aren't that great at swimming.

Any help would be greatly appreciated.