When one of the largest animals in the ocean takes a nap, it can look pretty weird.

Popular photos have surfaced online showing sperm whales gathered together, seemingly motionless and arranged vertically in the water. The whales, which are roughly the size of school buses, almost always appear to be "standing" and clustered in pods of five or six.

French photographer and filmmaker Stephane Granzotto captured this behavior while diving in the Mediterranean, where he was documenting sperm whales for his photo book on the creatures titled Cachalots. In the photo above, submitted to National Geographic's YourShot photography community, he noted that the whales had been napping for an hour.

A study published in 2008 in the