Like a lot of 17-year -olds, Zac Sunderland can get a bit tongue-tied at times. Only for Sunderland, it's not on account of hormones or nerves. "I've been out at sea for a long time," says Sunderland, who has nearly reached his goal of becoming the youngest sailor to single-handedly circumnavigate the earth in a sailboat. "You kinda forget how to talk. Sometimes I'll get into a port and it'll take a week before the words I'm wanting to say can come out of my mouth the right way. It's annoying." Sunderland, who has yet to get his driver's license,...