There are many animals living in the sea, but they are not all fish. For example, octopus is a mollusk, while whale is a mammal. There is also a strange appearance of animals called seahorses, their head shape is very similar to horses, so they are called "seahorses". But a horse is a true mammal, but a seahorse is not. Seahorses belong to the class Pisces, specifically Osteichthyes. Therefore, we can not judge the type of hippocampus by its appearance characteristics, and we can not mistake that hippocampus is not a fish, in fact, they are the real fish in the sea.
As mentioned above, although seahorses look similar to horses, they are not the same, because horses belong to mammals, but seahores belong to fish, specifically bony fish. Seahorses are taxonomically fish because they share some key characteristics with fish.
One of the more obvious ones is their respiratory organs. The special respiratory organ of fish is gill, which is different from that of other animals such as mammals. Seahorses breathe through their gills, and although their gills may not be easy to see, they do have gills as respiratory organs, which can be seen at close range. And then there's the way they operate. Fish generally have fins, and there are many kinds of fins, such as dorsal fins, caudal fins, pectoral fins and so on, and with the help of these fins can move freely. The same is true of seahorses, whose dorsal fins are relatively obvious, and which can only move freely through their swing.
