The ocean is full of mystery, not all of it marine in nature. Given the right conditions, some of that mystery washes ashore at random times, bewildering beachcombers, locals, and vacationers alike. The latest: A very large metal cylinder of unknown origin found on an Australian beach. And that's maybe the least of the weirdness. From strange sea creatures to macabre discoveries, here's what our seas have coughed up through the years.