California grunions know how to make the most of a beach vacation. When the tides are right, these silvery fish flop up onto the sand and go in search of a mate. Females burrow down and lay eggs beneath the sand while males entangle themselves around the females to fertilize the eggs.

Then adults head back to the ocean when the tides recede, leaving the eggs to mature. Inside a tough membrane that protects the egg and prevents it from drying out, a baby grunion can mature away from aquatic predators. It needs time underwater to wriggle free of its egg, so it waits to hatch until the sun and move perfectly align for the highest tide before dissolving its casing and swimming into the sea.