A heartbreaking, but very good read. I like how you tied it to the lecture at the beginning, and I always enjoy the little "twists of fate;" the at first seemingly innocent and inconsequential, or the "what's the worst that can happen" decisions (like venturing beyond a fence, or trying to walk across a log) that later (or sooner) turn out to have dire implications, or that one simple misstep that ends in tragedy.
That said, I have to say, I was really rooting for Abigail to survive somehow, even knowing from the start that she wasn't going to, but I know not every story can have a happy ending—I've written quite a few that way myself. If I had one critique, all throughout quicksand scene I kept screaming (inside of course) at Shawn: "Use the damn log! Just... crawl out on it, or push it her way or something!" But alas, people don't always think of the right solution in a stressful situation
Thanks for sharing, I enjoyed it! Oh, and welcome to QSF! I hope to see more from you soon.