You’ve probably seen one too many sci-fi films in which a crew happens to stumble upon a cave filled with slimy, green objects, but this isn’t what you think. Let’s just say that it’s from a real animal on Earth and it lives underwater. Continue reading to see more.

It’s an egg case that surrounds the fertilized eggs of some sharks, skates, and chimaeras. They are among the common objects which are washed up by the sea. They are made of collagen protein strands. Because they are lightweight, they are often found at the strandline, the farthest point of the high tide. The egg cases that wash up on beaches are usually empty, the young fish having already hatched out. Furthermore, egg cases are often found in commercial fishing gears like nets and pots, and on the sea floor during surveys using an ROV.