Ah, love in the animal kingdom. It’s not always happy or pretty, but every so often it is just. So. Cute!

Take the romantic little pufferfish (a particular variety of it, anyways), who creates beautiful, temporary designs on the ocean floor to woo the lovely lady fish.

For over a decade, no one actually knew what made these underwater beauties were or why, but finally a team of researchers tracked the little lovebirds down. LiveScience notes that “[a]lthough the fish are only about 12 centimeters (5 inches) long, the formations they make measure about 2 meters (7 feet) in diameter.” That’s a big sandcastle for a little fish to build!

And it has to be a good sandcastle! The lady fish will come and inspect the male’s handiwork before deciding if she’ll mate with him. If the castle is a winner, they’ll lay their eggs in the center of the pattern, where the pattern itself creates an ideal environment – the ridges on the outside protect the silt in the middle where the eggs are cradled.

For more details, check out the LiveScience article and the video below!