I learned today that sharks have rather interesting vision. Many species have both rods and cones, and they demonstrate an excellent ability to detect contrast. Like cats and other night animals, sharks have a tapetum lucidum, a layer of mirror-like crystals behind the retina which enhances vision in very low light. Apparently sharks hunt primarily by sight, even though they are also sensitive to vibration, electromagnetic fields, and chemical changes in the water. Tiger Sharks have a clear membrane that can cover their eyes like a see-through eyelid while on the attack. Tiger Sharks, like tigers, are one of the few animals that view humans as food. (Great White Sharks will attack humans, but they haven’t actually acquired a taste for us.) They are predators with superb vision, particularly in the watery depths.
In my book, Divining with Animal Guides, I write about the eyesight of many animals and how that applies to divination.