The body

A fish is typically drawn as an elongated spindle, and in fact this is the most common form, as it makes it easier to swim in open water. These hydrodynamic characteristics permit rapid acceleration and not inconsiderable speeds (sometimes up to 20 km per hour) in a medium (water) that offers a certain degree of resistance.

Hippocampus kuda.

However, there are other forms, that are also all connected with the lifestyle of the fish in question: bottom-dwellers have a flat stomach, while those that live in water obstructed by plants and branches have compact, thin bodies that enable them to squeeze through the obstacles. This is equally the case with the countless fish in the coral reefs, which thread their way through the blocks of coral. Finally, there are certain fish that are unclassifiable, so varied and strange are the forms they flaunt, although they always correspond to a particular lifestyle.