Praia de São Martinho do Porto

São Martinho do Porto, a seaside town in the municipality of Alcobaça, is built around one of the most unusual beaches in Portugal. VisitPortugal describes about 3 km of sand curving round a sheltered bay in the shape of a shell, which locals call the Concha. The sea is calm, and the tourist board says it offers excellent conditions for children and for water sports such as windsurfing, sailing and canoeing.

The Portuguese Environment Agency (APA) goes further. Its official description of the bathing water says that the bay, because of its shape, is especially good for children.

Turismo Centro de Portugal explains that the bay formed as an old lagoon gradually silted up. The APA calls it the remains of an ancient gulf, and says the bay opens to the ocean through a mouth about 250 metres wide, between the Santana hill to the south and the Farol (lighthouse) hill to the north. In the 12th century, the tourist board adds, nearby Alfeizerão was an important seaport, which gives children a sense of how much more water there used to be here.

Waves arriving from the Atlantic have to squeeze through that narrow gap and then spread out across the wide, round bay. By the time they reach the beach, most of their energy is gone, which is why the water inside is so much calmer than the open coast a few hundred metres away. It’s a geography lesson you can see from your towel.

It’s the classic Silver Coast answer to “where can small children paddle in the sea?” The APA doesn’t flag waves of special value or rockfall at either part of the bay, and both have lifeguards in the bathing season.

The usual rules apply: keep toddlers within arm’s reach, swim between the flags, and keep an eye out for sailing boats, windsurfers and canoes, which share the bay. Don’t let children head out towards the mouth, where the water from the open sea comes in.

São Martinho do Porto’s 2026 bathing season ran from 13 June to 13 September. The APA divides the bay into two beaches, Sul (south) and Norte (north), both lifeguarded. The southern beach flew the Blue Flag in 2026 and is listed as accessible with an amphibious chair.

The APA rates the water “excellent”, and the last analysis of the season, on 18 August 2026, was rated suitable. Its profile notes that the Rio Tornada, which drains into the bay, can carry pollution after heavy rain, for a day or two at most. There were no days of bathing advised against in 2025.

VisitPortugal lists lifeguards, umbrella hire, light boat hire, showers, parking, bars and restaurants. The APA adds toilets, a first-aid post and beach support services on the southern beach.

Turismo Centro de Portugal describes a seafront promenade (marginal) that runs along the whole beach and calls the town a classic place for a family stroll, lively in the bathing season. The town was founded by the monks of the Alcobaça monastery in the 13th century, according to VisitPortugal, and grew into a popular resort in the 20th century. Its restaurants are known for seafood such as lobster and stuffed spider crab.

The same calm water that suits toddlers suits beginners on boards and boats. VisitPortugal highlights windsurfing, sailing and canoeing, and lists light boat hire at the beach. Older children who have outgrown paddling can try something new without Atlantic surf to deal with. Ask at the beach about lessons and hire.

It’s popular, so August weekends are crowded and parking gets hard. The water is still cold: VisitPortugal puts the average summer sea temperature at 17 to 19°C. There’s no natural shade on the beach itself. And because the bay is shared with boats and boards, children swimming further out need watching.

North up the coast, Nazaré has a big town beach and the Forte de São Miguel Arcanjo above the giant waves of Praia do Norte. South, the calm lagoon beaches at Foz do Arelho and Bom Sucesso make a good contrast, and the walled town of Óbidos is inland from there.

Is São Martinho do Porto good for toddlers?

Yes. The APA’s own description singles the bay out as good for children, and VisitPortugal describes a calm, sheltered sea.

Why is the water so calm?

The bay is almost closed. The sea comes in through a gap about 250 metres wide between two hills, and the waves lose their energy as they spread out inside.

Is there a lifeguard?

Yes, on both the south and north beaches during the bathing season, which ran from 13 June to 13 September in 2026.

Is it wheelchair accessible?

The southern beach is listed by the APA as accessible, with an amphibious chair.

How cold is the water?

VisitPortugal gives an average summer water temperature of 17 to 19°C.