Fishing rods are able to fish outside of water.

To recreate:

1. Create a floating water block using /setblock with minecraft:moving_piston surrounding it
2. Put a block right next and a bit above to set the bobber in position
3. Send the fishing bobber into the block, it will fall in the water
4. Wait for the fish to catch multiple times
   • Each time the fish gets caught on the bobber it sinks by a little each time
5. When the bobber sinks it will fall to the ground, then you can right click to get the item.

https://youtu.be/B3ST_59ZkGk