Heal the Bay’s Santa Monica Pier Aquarium will hold its fourth annual Underwater Parks Day, celebrating the implementation of Marine Protected Areas (MPAs) in Southern California, from 12:30 to 5 p.m. Saturday, Jan. 21.

The event will feature activities and presentations about the newly designated areas and give visitors the chance to meet many of the marine animals they protect.

Visitors will receive a free canvas tote bag and can create their own underwater parks scene on their bags at the aquarium’s craft station. There will also be a variety of interactive games and activities as part of the event.

Aquarium admission will be free Jan. 21 for those who first join a beach cleanup and/or nature walk from 12:30 to 2 p.m. at Westward Beach/Point Dume.

Information, (310) 393-6149, or www.healthebay.org/event/underwater-parks-day-our-aquarium.