Whenever I see this picture I think of this:
| Creature | Swims | Walks | Flies |
| -------- | ----- | ----- | ----- |
| Dog | X | X | |
| Fish | X | | |
| Bird | | X | X |
| Duck | X | X | X |
Notice how for each combination of swimming, walking and flying, there is a living creature that can do just that, with the exception of swimming and flying.
Sure there are flying fish, but they glide rather than fly. Did evolution really forget to cover this niche?


Considering that I am including a snake’s movements in “walking” in this context, I’d say that’s good enough.
Honestly though, considering 2/3 of the planet surface (and increasing) is water, one would think there would be some answer to this, but I suppose it has something to do with the physics of it…
So I think that the air-time of flying-fish is optimised more than enough for such a purpose and that the birds that we see diving to get food are more from the evolutionary route of - land animals that can fly, adapting to get food from deeper into the water.
I’m finding this discussion so interesting! It’s honestly something I’d never thought of at all, but it’s an excellent exercise for my brain. Gannets have evolved special protection for their brains when diving, btw. They hit the water at 60mph. I wish we’d evolved some cooler attributes than opposable thumbs and walking upright. Gills, for example. Ah well.