They're less than an inch long. They can change color. They're called Pygmy Seahorses and they're nearly invisible.
The coloring on the seahorses can vary from bright red to dull grey, depending on the coral to which they anchor.
In order to hold onto the strands of coral, the pygmies have prehensile tails, like some species of land mammals and reptiles.
Though their name and appearance suggest otherwise, pygmy seahorses are a species of bony fish, related to bass or salmon.
Because they are so small and well camouflauged, many seahorses were only discovered within the last ten years, so there is still much to learn about them.