A favoured spot for Lisbon surfers when swell doesn't wrap into the city breaks, Guincho is a long, open beach that is rarely flat, but it's also exposed to wind - hence its popularity as a summertime windsurfing haunt. It does produce quality waves though, working best on lower tides when long, reeling lefts and rights can form around shifting banks. Gets big and is famed for its brutal rip currents.
Source: Praia do Guincho Surf Guide