When a humpback whale began playing with Nan Hauser like a toy, she feared the worst. The 50,000-pound mammal swam toward the marine biologist and began to nudge her. Nan had been deep-sea diving for 28 years, but had never known a whale to be this touchy-feely. It appeared hell-bent on throwing Nan on its head and back. Most of all, it wanted to tuck Nan under its pectoral fin.