Some water animals have flippers. Flippers can act like an airplane wing in the water. The sea turtle, sea lion and seal are examples of animals with flipppers. The movement of the flippers allows the animal to go up or down or forward in the water. Sea turtles and sea lions use their front flippers to move forward.
Seals use their tail flippers to move forward.
The simplest example is the jellyfish. These animals fill their umbrella section with water and then push the water out. The jellyfish then moves in the opposite direction. But, there is no control over the direction. A squid does have control.