Water Beasties Across the Seven Seas

Water, water everywhere, and mysterious beasts in all of it! Each time we think there's nothing more to be revealed in the depths of our oceans, something new and surprising comes out of it, maybe in the form of something that was assumed to be extinct thousands of years ago, or something with its only known relatives 500 million years ago. Our planet's been explored ever since time immemorial, fr...