Penguins are birds of the sea, at least those which have the sea as their primary source of food, those who spend a great deal of time swimming in it, living their lives in it.
But is that not the same situation the whales' ancestors found themselves in? Trapped between two elements? Dependent upon them both, occupying not one, but two nisches in the natural chain of life. Eventually, the ancient whales made a decision, to stay in the water. What are the penguines going to do?
My thoughts are that the penguins eventually will do the same. And I am sure that most of you agree. Watching the penguines agile, swift movement in water; almost like chubby but yet well-adapted fishes in the great blue sea.

So, this is my thoughts of what a possible whale-ified penguin would look like, before they have fully adapted and specialized trheir bodies for the new surroundings.
I had a few doubts however the fin/wings would be longer than they are now, or shorter, and even broader/thinner. After a while, I settled with these, long/thin, wingfins, but they would probably be even broader, as penguines use their wings in order to gain speed in the water. I see no reason why they should change that, so I focused on that. That is also the reason for why the back fin/feet are a little smaller, because they do not use it as much, even if I guess, that it most likely will become even smaller, just because of that.
The nostrils are located higher up on the beak, as they breathe like whales do.
The tail has turned into some kind of fin on the back, helping the pengale to keep its balance in the water during high speed hunts.

This is my picture of a possible future of the penguine species, but also an attempt from my side to come up with a bird, acting like a whale, living its whole life in the sea. Beacuse the mammals have their whales, the reptiles have their snakes and crocodiles to some extent. The amphibians are dependent on water, the fish cannot live without being surrounded by it. Even the insects and spiders live in it!
So why not the birds?

I started this picture out in a small size, even with the details, so when I realized that it was too small in size, I was not really motivated to start the whole picture over...