Most marine organisms swim by pushing water behind them. This can be done with a variety of body structures, including fins, tails, and flippers. Some organisms, such as jellyfish and sea urchins, use cilia or flagella to move through the water.

The number of limbs that a marine organism has does not necessarily determine how it swims. For example, fish have paired fins that they use to push themselves through the water, while whales and dolphins have flukes that they use to propel themselves forward. Some marine organisms, such as sea turtles, use their limbs to paddle through the water.

Some marine organisms have special adaptations that help them to swim more efficiently. For example, dolphins have a streamlined body shape that reduces drag, and tuna have a series of keels on their bodies that help to stabilize them as they swim.

The ability to swim is essential for many marine organisms. It allows them to find food, avoid predators, and travel to new locations.