If you don't mind the heat and you're as in love with the ocean as I am (Mercedes), South Padre Island, TX is the perfect spot. You can volunteer with the local sea turtle non-profit, http://www.seaturtleinc.org/, or you can relax on the beach with a pina colada. It's a great place to enhance you marine flora and fauna vocab, or just hang out for a while.
One of our close friends, Shelby Bessestte, is currently working towards her dream of being the next Sea Turtle Lady, so she can spend her time promoiting coastal protection and sea turtle conservation. Check it out: