MIT’s Edgerton Center holds free Science on Saturday program about monthly for elementary, middle, and high school students — as well as their parents and teachers.  On December 6, the program will be focused on underwater robotics (PDF), presented by the Edgerton Center’s Marine Robotics Team.  Kids under 12 must be accompanied by an adult.  The program includes a one-hour presentation at 10AM followed by hands-on activities at 11AM.  No pre-registration is necessary but seating is limited and first-come, first-seated.  It’s held in MIT’s Kresge Auditorium, 48 Massachusetts Ave. in Cambridge.