Panoramic view of the white sands of Praia Grande, the largest beach on the Sintra coast, with the Arribas Hotel's seawater pool, the largest in Europe, Sintra Coast, Portugal, Europe

Praia Grande, the largest beach on the Sintra coast, white sand, and popular with surfers, with the Arribas Hotel's seawater pool, the largest in Europe, Sintra Coast, Portugal, Europe

Praia Grande, the largest beach on the Sintra coast, white sand, and popular with surfers, with the Arribas Hotel's seawater pool, the largest in Europe, Sintra Coast, Portugal, Europe

Porco's bay and Dois Irmaos islands, Fernando de Noronha national marine sanctuary, Pernambuco, Brazil (S. Atlantic)

Seawater swimming pool at Reid's Palace Hotel, Funchal, Madeira, Portugal

Indoor seawater swimming pool on the beach of the Baltic resort Laboe, Kieler Bucht, Schleswig-Holstein, Germany, Europe