MUSIC BY THE SEA: 6 to 9 p.m.; St. Johns County Pier Park, 350 A1A Beach Blvd., St. Augustine Beach; admission free, meals $10 or less. For information, go to sabca.org. Grapes of Roth will play classic and alternative rock. The food vendor is Mellow Mushroom.
NATURE PHOTOGRAPHY WORKSHOP: 6:30 p.m.; Nease Beachfront Park, 3173 Coastal Highway; free. To register, call Kelly Ussia at 904-209-0335. Join local photographer Nicholle Goodnight for three hands-on workshops to sharpen skills. Participants need their own equipment and should be age 12 and up.
WEAPONS DEMONSTRATIONS: 10:30 a.m., 11:30 a.m., 1:30 p.m., 2:30 p.m., 3:30 p.m.; Castillo de San Marcos, 1 S. Castillo Drive; $15 adults, free for children. For information, call 904-829-6506 or go to nps.gov/casa.