whales are the evolutionary equivalent of pulling a u-turn on the freeway
>start evolutionary journey in The Ocean
>grow legs and learn to breathe air, leave The Ocean
>say nvm, go back to The Ocean, sometimes keep the hips? and they just. float there.
>continue needing to breathe air, which is in short supply in The Ocean, Where You Live, so you evolve to hold your breath really long, but you still have to come up for air
>good job whales, you dipshits