“Not garbage! Not an alien!” the Seaside Aquarium posted on Facebook recently. “It’s a giant marine snail egg casing!”

Fully grown, the Lewis’ moon snail can grow up to 5.5 inches. The Washington State Department of Ecology calls it a “voracious predator,” whose favorite dinner is clams.

The snail is a “clampire,” using its big foot to engulf and grip the unsuspecting clam. Then, the snail uses its toothlike radula to drill a perfectly round hole into the clam, which takes up to four days, as it can only drill about 1/64th of an inch a day.

However, the snail speeds up the process a bit by producing hydrochloric acid and enzymes to help dissolve the clam’s shell and liquefy its innards. Then, the snail inserts its tubular mouth and enjoys a liquid lunch, which can take a day or so to digest.

“Lewis’ moon snails … prowl the intertidal zone down to depths of 600 feet … Held together by mucus and sand, the developing embryos are laid carefully in what is called a ‘sand collar’ (pictured),” the post reads. “When you’re beach combing, keep an eye out for these freaky colonies of developing, future super-sized gastropods!” (Photos: Seaside Aquarium and Christian Gronau/Cortes Museum & Archives)