Do penguins fly (under water)?

You may be familiar with this meme. That when penguins swim under water, the motions they do and the physical principles in play are more similar to flight than to swimming. Is this really the case? Is the swimming of penguins flight in a denser medium? Is the distinction even a relevant one?

I wasn’t aware birds were able to propel themselves through the air with their feet.

Flight and swimming are essentially the same thing - propulsion through a fluid medium. I don’t know how you can have a motion that’s more similar to one than the other.

I would say yes.(youtube video)

Interesting yes, relevent, probably not. Penguins propel themselves with their wings, which looks much like flying. Fish seem to propel themselves mostly by using their body to move their tailfin from side to side, which I find less graceful.

Penguins use their wings for their main source of propulsion under water, not their feet.

Everybody in this thread appears to be forgetting the fairly basic difference between floating and flying. Do you think that if a penguin folded its wings underwater it would plummet to the bottom of the sea?

Like smeghead said, flying and swimming are, on one level, the same action. However, I think a distinction could be made between situations in which the flyer/swimmer is approximately neutrally buoyant, and those in which it/he/she is not.

I’d be tempted to call swimming the act of moving through a fluid in which one’s own density is approximately that of the fluid (i.e., nearly neutrally buoyant). You need to expend little energy to maintain “altitude” - position in space parallel to the gravity vector - and can thus exert almost all forces in the direction one wishes to move. A human immersed in water, for example.

Flying, on the other hand, could be said to require considerable effort merely to remain stationary in “altitude”, while actual motion in the desired direction is superimposed on that.

Now, drawing the dividing line between the two is going to be somewhat arbitrary (pick a density ratio), and there’s sure to be a transition region. But I think what the OP is referring to is the pretty clear differences in motions required when one is nearly neutrally buoyant versus when one is very much not.

Actually, I wonder if it might shoot to the surface - which would require them to “fly” in the other direction. Do penguins have enough air trapped in their feathers to make them positively buoyant, perhaps? (I really don’t know, but the way they “swim” sure looks to me like they’re fighting gravity effect, too.)

Penguins float like a cork. The have a lot of blubber as well as air trapped in their feathers.

[ETA: Responded to brad_d’s post]

That makes a lot of sense and is in line with what I was thinking. Fish float in water and propel themselves with their fins. In that sense they are closer to a blimp than to a plane.

I have no idea whether penguins would float or sink if they stopped propelling themselves. Even if they floated, can they control their buoyancy and move up/down the water column without propelling themselves? [ETA: answered while I typed]

A possibly relevant case is that of sharks. I seem to remember that they could not control their buoyancy as they have no gas bladder as bony fish do. They have to swim up or down as opposed to floating up or sinking down as bony fish. Not only that, but that they tended to sink and the shape of their body helped keep them afloat when they moved forward. I am not sure how this makes or breaks the tie between swimming versus flying but it might be a useful example of the gray area in between.

OK, so penguins mostly use their wings for propulsion.

They are close to neutrally buoyant, so they aren’t using their wings to generate a large amount of lift during cruise.

They probably use their wings for roll control.

For pitch control, how much are they using their wings, and how much is their body behaving as a lifting body?

Suppose you’re a penguin. You’re cruising flat and level. You want to turn left. You use your wings to roll 90 degrees to the left. Then you:

A) rotate both wings to a higher angle of attack, or

B) tilt your head back to shape your body into a fat, feathered banana that arcs through the turn without much lift from the wings.

So is it A, or B, or a little of both?

Yep, its all fluid dynamics at a certain point. Someone could conceivably make an airplane that works just as well underwater or in space, for that matter.

This sub here works a lot like an airplane:

So, where do we stand on this one?. It seems that swimming (as fish do) is comparable to blimps while flying (as birds do) is comparable to airplanes. Are penguins blimps or airplanes?

Penguins use the same basic “flight stroke” for swimming as their more volant cousins use for flying. The wings are thus used for both propulsion and maneuvering (with feet and tail feathers assisting to some degree here).

Note that this is different from how, say, a humpback whale propels itself through the water, which largely uses its tail fluke for propulsion and the large “wing” flippers for stabilization and maneuvering.