Has anything like this happened in the evolution of animals?

Has any flying creature (e.g. a bird) evolved into a sea creature that permanently dwells on water, like whales do? According to the theory of evolution, much of today's life originated from primitive, sea creatures of the deep past. Now, I am aware that some of these never left the waters, some others evolved... show more Has any flying creature (e.g. a bird) evolved into a sea creature that permanently dwells on water, like whales do? According to the theory of evolution, much of today's life originated from primitive, sea creatures of the deep past. Now, I am aware that some of these never left the waters, some others evolved into land animals and stayed on land, while others evolved into land animals, but went back to the water to become sea creatures again (whales, dolphins, porpoises, seals, manatees, dugongs...)
Has any sea creature evolved into a bird and, eventually, into a sea creature again?
Update: I am not talking about semi-terrestrial or semi-aquatic animals, but about fully aquatic animals
Update 2: I am talking about an animal of true flight that has evolved into a fully aquatic animal
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