Ok, so yeah... This "game" is still far from the point and I read your game description. Also, I want to include some aspect and problem in the game that may help you in fixing those faster (if you still want to update the game.
Problems:
1. The game is at this moment more of an "walking simulator during winter" than a game about fishing, but to be fair you mentioned it in the description already.
2. The left mouse button is a problem as you said if you hold it (also because I know some things about godot maybe "insert.is_action_just_pressed()" may help in fixing your problem.
3.The game is really power consuming... My device had to start up it's fans to cool of and that without spawning any fish so there must be some fixes and optimizations in the game for the moment,
4. Mountains and mostly anything has missing colliders...
5.When you try to enter on one of those ice sculptures in you look a bit down you can see the interior of the character head.
6.At first, the camera didn't wanted to rotate after entering the game for the first time. After re-entering everything seemed to work fine.
So... Fine base for a game. Not a really complex one, but it need a bit of work for it to be ready, so good luck !!!
Also, my personal ratings for the game are :
Creativity : 3 out of 5
Functionality : 1 out of 5
Enjoyment : 2 out of 5