Great beach with nice sand and supposedly not as busy as other beaches during July and August. It's about 2km/ 1 1/4 miles long and sits in a bay. At low tide it's even longer since you can get around cliffs to the east.
There are also cliffs that you can walk up to the east and wet to get great views. To the east you can walk to Ponte de Piedade in about 35 minutes with only the initial climb up the cliffs being strenuous. To the west you can walk the cliffs to Luz although the climb down is a little treacherous.
There are also two restaurants at the beach O Antonio and Campimar which are reasonably priced even when you don't consider the premiere location.
There's even bus service from Old Town if that's where you're staying. read more
This is definitely the best beach in Lagos. Not only is it quiet and stunning, but it's easily accessible with plenty of free parking. Many beaches here are difficult to get to by foot, but this is a breeze. The cliffs are beautiful. read more
This is go-to beach for most of the locals here in Lagos. Not as long as Meia Praia this beach has the advantage that regardless of the weather / wind direction it is always nice. This is especially true because of the usual North wind that makes Meia Praia impossible to stay at with sand storms all over the place.
Porto de Mós has a lot of families as well so if you want some quiet during July and August walk all the way to the right towards the end of he beach. Bonus points if you find the natural mud ponds ;) read more
This is by far the best beach in Lagos. You aren't surrounded by the cliff faces and rocks which is a shame, but the sand is lovely, there is plenty of room for everyone, you can rent sun loungers and beach umbrellas, people walk around selling water and ice creams, there isn't as much seaweed as you get at other beaches. I loved it. read more