Orlando-based Aquatic Design & Engineering Inc. has built multimillion-dollar fountains and resort swimming pools all over the globe, as well as for Central Florida's major theme parks. Here we asked the firm's president, Josh Martin, to give some insight into the 27-year-old business, including what keeps him up at night and industry opportunities he sees coming down the pike: What do you love most about your job? That I don't know what tomorrow is going to hold. Every day is a creative challenge. What…