Ribbon eels start their life as male black eels, change to male blue when adult and at a last stage they become yellow females
Pygmy seahorses stay on the same sea fan their whole life and might only move around in a plate sizes area
Dolphins can technically see through other animals! The high pitched sound they produce for echolocation only rebounds of hard surface such as bone and cartilage, but passes through soft tissue. This allows them to see (or more accurately, hear) through other animals!
Gulper eels have this unusual adaptation like pelicans that allows them to scoop up water into its mouth to swallow prey whole. They primarily feed on crustaceans, fish and cephalopods, but some scientists believe their wide mouth allows them to go after larger fish if food is hard to find.
The Amazon pink river dolphin is the subject of many South American folklore, not all benevolent. One such legend claims that the dolphins morph into handsome men known as "boto encantado" to seduce and impregnate womenfolk by night. Another claims that if you go swimming alone, the dolphins may whisk you away to a magical underwater city, which has led to the local fear of going near the water between dusk and dawn, or entering water bodies solo. Some also believe them to be the guardians of the Amazon manatees, so those who wish to see a manatee must first reconcile with the pink dolphin. It is considered bad luck to harm the dolphins, and even worse luck to eat them.
The chimaera is a strange fish that has a network of lines over its surface. The lines often look like seams that give the impression that the animal's body has been created by stitching together parts of other creatures. The appearance is reminiscent of the chimera, a creature in ancient greek mythology whose body consisted of parts of different animals joined together
The 2004 Sumatra-Andaman earthquake in the Java Trench caused a sufficiently massive release of energy to alter the Earth's rotation, shortening the day by 2.68 microseconds. Similarly, the Tōhoku-Oki earthquake shifted the Earth's axis by between 10cm and 25cm, shortening the day by another 1.8 microseconds.
Horseshoe crabs are not crabs at all. They are not even crustaceans. Instead, they have their own separate class named Merostomata. They have hardly changed since the age of the dinosaurs, and their closest-living relatives are spiders.
Pea crabs measure between 7 to 8 mm in width. They're so small that they actually live as parasites on other shellfish, like oysters, clams, and mussels.
To survive, Antarctic fishes have developed proteins that act as antifreeze. These antifreeze proteins are a group of unique macromolecules that help some polar and subpolar marine bony fishes avoid freezing in their icy habitats.