What is the ruling on praying behind an Imam whose open transgression is manifest by swimming in places crowded with female tourists who are semi-naked?

Congregational prayer behind a fasiq (open sinner) imam is valid according to the majority of scholars. It is obligatory to advise him and clarify the danger of his actions, and that his actions are uglier than someone who does not lead prayers. If he does not respond, it is preferable to seek a just imam, for praying behind a fasiq is disliked (makruh) by the agreement of the imams, and to avoid the disagreement of those who invalidate prayer behind him.