How do fishes move in water without streamlined body structure?

Question

How do fishes move in water without streamlined body structure?

Answer 1

well...

let's say that the fish is a flat paper.

then to move it self it will do something like this

do not mind the punctuation marks.

i do not have any other pic

----- to this ~~~

it can form bends to push the water behind and to propell itself forwards.

^_^