This feels like a good start for a fishing mini-game. The core mechanics are in place and work pretty well.
The biggest thing that stood out to me is the delay between pressing the left mouse button and the fishing rod showing. It would be good to show something right away to give the player feedback that what they did had an affect. If you want a delay before the fishing starts, maybe try showing the rod angled backward, and rotating forward as if casting. Adding a bobbing motion to the rod, or something floating on the water, would also add a bit of feeling like something is happening.