How does fishing work?

[Lupich]

I see lots of fish jumping in the water, I'm standing on the shore and can cast a line to where they seem to be.

What do I do next?

Do I have to click at the right moment, or is it passive?

[Saxony4]

You need bait to be able to fish, entrails from butchering small critters will work, worms work as well.

Fishing is passive and the timer will go down and repeat as you fish, though you may not get a fish every time the timer resets.

[MagicManICT]

Any bug you can find works, ants and silkmoths included