Perceptions of lifeguards and beachgoers facing emerging cyanobacterial blooms washing ashore

• We applied a mixed methods approach to study perceptions and potential behaviors towards cyanobacterial blooms. • Lifeguards are strategic actors to anticipate and adapt to blooms, but still need more training and support by institutions. • The presence of the health flag is not the main factor influencing beachgoers behavior when cyanobacterial blooms occur. • Age, perceptions, distance, water activity, and having children are relevant variables to predict beachgoer behavior class. • An approach involving government intervention, research and effective communication is needed to improve the system response.