Well, not exactly free. Costs you $10 to enter images to the 'Oceans of Life' photographic competition. The winning image wins a trip to Antarctica with Aurora Expeditions.
Visit http://celebrateourseas.co.za/competition/ to logon and submit images of any marine life. Any profits go to support BirdLife South Africa's seabird conservation work.
Please spread this to your personal contacts. Competition closes for entries 5 September, and like everything nowadays, terms and conditions apply...