D: OK, Yael, you want to build an aquatic robot,and you're trying to figure out the most efficient way to move it through water, what do you do?

Y: I am guessing the answer isn't to build a robot using a lot of root-force to move forward?

D: Anyone who has tried walking or running in water knows how much effort that can take compared to swimming, which by the way is a hint.

Y: It is?

D: Look at the fish, my friend. Many fish after all, live in turbulent waters.

Y: I see where this is going. Over time, fish have made adaptations to conserve energy when swimming against the current.

D: And researchers at Harvard figured out the underlying physics.

Y: So they literally understand what it means to swim like a fish?

D: Yes. You see, when water hits objects like branches, rocks, or other fish, it forms strings of little whirlpools, or vortices. So researchers set up a tank with water flowing in one direction, and dropped a cylinder in it that generated vortices.

Y: So what did they find out?

D: The researchers observed that rather than fighting the current, the fish simply slalomed between vortices, using a swimming style that resembles a flag flapping in the wind. The advantage of all the side-to-side movement is that it requires very little muscle activity. In fact, fish can use this technique to hold their position and rest while in rough patches of water.

Y: I bet that comes in handy for swiming up a fish letter.

D: These findings have applications ranging from technology to conservation.

Y: And it gives us a whole new dimension of what it means to swim like a fish.