What do the beach flags mean and what about rip currents?

Only swim where lifeguards are on duty and watch the flags. In the Brazilian system, red over yellow marks a guarded swimming zone, red means high risk, yellow caution, green calm sea and black no lifeguard cover. Rip currents show as darker, wave-free strips: if you get caught, stay calm, don't swim against it and wave for help. Emergency number for rescue: 193.

Source: parana.pr.gov.br