A far cry from the highly stylized square fish we learn when we were young, the fish actually have an abundance of bizarre shapes. Fins are one of the main drivers of underwater locomotion in open oceans, sandy bottoms, and reef crevices. But let's take a step back first. Fish not only have a pair of fins, they have seven. A dorsal fin (below the back), two pectoral fins (one on each side), two pelvic fins (both in the middle of the bottom), an anal fin (behind the bottom) and, of course, a caudal fin. Each fin contributes to the fish's ability to survive and navigate its environment. Given the myriad of marine environments and challenges, fin morphology has evolved to suit a fairly wide range. We humans enjoy the ocean and do our best to enhance our specially designed swims, but ask any snorkeler or scuba diver he finds fish glide effortlessly through the water, almost flying. I would definitely agree that it looks like it. Indeed, swimming can be compared to flying, with studies showing strong similarities between the optimal aspect ratio and the angle of incidence for efficient advancement. Fish fins not only propel the fish forward, but also prevent them from sinking or swimming in the process. The C-shaped tail is optimized for explosive speed and is characteristic of open water predators such as marlin, tuna, swordfish and sailfish. Deeply forked tails, like pompanos and pearlfish is useful for swimming at a more relaxed speed. Rounded fins allow for a very short thrust and great maneuverability. A school of fish like a sergeant I use pecks in groups, but thanks to the rounded fork tail shape I can jump quickly when I need to. Rounded goby-like fins Helps fish burrow into the sand and is suitable for slow bottom dwelling lifestyles. The shape of the fins also helps fish to be competitive in complex habitats such as reef debris. This ability to turn quickly and sharply allows evasive maneuvers and effective use of available cover. Wrasse and Butterflyfish often uses this method. Some fish are even hiding in crevices. The triggerfish is named for the "trigger" or spine just before the dorsal fin that flaps when a fish finds a hiding place. This thorn lifts up and the fish's head digs into the cracks in the rock, making it impossible to remove the fish. Such fin adaptations act as a defense mechanism against dire situations. Other notable modifications to their fins include the famous flying fish, which prolongs its glide out of the water with its large pectoral fins in order to "fly" when danger is imminent, and the ugly fish, which waddles across the ocean floor with modified pectoral fins. Support the fish from the bottom. Its fins even resemble fingers. Another common use of dramatic fin changes that often compete with impressive locomotion is signaling. Tall dorsal fins, filaments, flourishes, and dramatic coloration help signal (or remain unnoticed) to mates, rivals, and predators. Because the pectoral fins can flap or flash color signals at will, warning coloring and mating indications can be worn as needed when on the surface of the fins. In such competitive marine environments, the utilization of fin modifications has repeatedly improved fish species fitness, creating both beautiful and bizarre morphologies across diverse marine fish trees.