Was just going to say what Tommy said ... Sifnos is a gem. I stay up on the hilside, with a view out across a valley to other hills and out to sea. My secret gem is Nikoleta's APts. She has 2-3 of these, vine-covered front patios, little breakfast-corner in main room, comfy beds... and she is adorable. https://gerontisifnos.gr/en/home/ Tell her Janet From Philly sent you... I have watched her son grow up, adorable family; husband has a taxi... she'll gift you tomatoes from her garden out front.
If these 3 are taken, she also now runs her parents Geronti pension right next door, 4 rooms or so on a loooong shared balcony-patio with same view. https://www.thesaurus.gr/hotels/sifnos/apollonia/geronti_pension/geronti_pension.php If all these are full, the Aegean Thesaurus agency is Marvelous -- It started on Sifnos, now covers all greece, but still maintains office right at port. Check its website -- you can sort its accoms by town AND by price. They have a lot of cute "mom & pop" pvt apartments up in the hills, that don't have websites, because they don't want the fuss & don't speak much english; only work thru Thesaurus. I found a couple of great ones like this for a couple last year.
For swims, Take good bus service down to the beaches (I favor Vathy or Platy Gialos, I think Faros has brown sand, not my fave)... nightlife up in appollonia is vibrant.... good music, chic people. Kamares, the port town has lots going on of an evening.... you could take the bus down there, and taxi back uphill at bedtime. Some people (mostly Brits) seem to like staying there, but the ONE road to everywhere is always filled with traffic, and I think the beach is meh... too close to ferry pier. Kamares faces west for sunset, but is wedged in the fork between 2 very high hills, so always feels closed=in to me. Just my opinion. Good luck!
You may want to rent a car for 1 day to zoom around everywhre... lots of good hiking, but in August you'd have to do it 7 am or so...( Beth, why August??)
