One of the many fossil creatures visitors will encounter in “L.A. Underwater,” this extinct ammonoid (Eupachydiscus) swam through Los Angeles 74 million years ago when large dinosaurs still roamed the coast of Southern California. (photo courtesy of the Natural History Museum of L.A. County)

The Natural History Museum of Los Angeles County will present “L.A. Underwater: The Prehistoric Sea Beneath Us,” opening May 2.

The multimedia-rich, immersive exhibition explores the underwater realm of prehistoric Los Angeles when much of the L.A. area was submerged beneath the Pacific Ocean. Visitors will view rare fossils from across the L.A. region and encounter huge cinematic elements showcasing sharks the size of school buses, glowing deep sea fish, giant tuskless walruses, a 10-million-year-old whale skull discovered in Lincoln Heights, and other awe-inspiring species that roamed ancient L.A. The two-year exhibition will feature engaging media elements that bring fossils to life and serve as reminders of the ancient ocean that is still shaping L.A.

“With ‘L.A. Underwater,’ we are giving visitors an in-depth look at the Southern California region, millions of years before humans set foot anywhere near Los Angeles. Through NHM’s commitment to discovering the natural world in our own neighborhood and this exhibition’s focus on our extensive marine collections, we continue to shape our understanding of the ancient past as well as inform current and future discoveries,” NHMLAC president and director Lori Bettison-Varga said.

The exhibition also features the skull of a newly-described giant walrus species, Pontolis Barroni, never before seen by the public. The exhibition features nearly 40 fossils and specimens showcasing the Los Angeles region’s vast pre-history, including an ammonoid fossil that dates from nearly 75 million years ago, the 13-15-million-year-old Coursen’s Strange Seal, a 10,000-50,000-year-old saber-toothed cat skull and a shell discovered in modern L.A. soil.

“L.A. Underwater” is free with museum admission. The museum is located at 900 W. Exposition Blvd. For information, visit nhm.org /underwater.