Just 1.5 million years before humans began taking leisurely dips in the ocean, the waters were home to an immense shark "Megalodon" (formally known as Carcharocles megalodon). Despite coming in at more than 60 feet long, young C. megalodons would still have been vulnerable to other predators of their time, much like young great whites are today. According to a new study published in PLoS One the "mega-toothed shark" may have protected its young by delivering them in nurseries.