I played it completely without encountering any bugs. Very nice work, especially if you're still new to coding! I'll agree with some of the other feedback: if you let me run to the right and shoot the musket as quickly as I wanted to, and especially if you let me shoot it as many times as I wanted to, I think it would be even more fun! I also found it a little unintuitive that if I press down multiple times, I still hear a sound effect for movement even though I'm not actually moving. That seems like it might be an easy fix.
I love the concept of bonding with your grandfather on a fishing trip and encountering something particularly dangerous and out of the ordinary to add some drama. If you want to keep developing this further, I think there's a lot of room for being able to choose dialogue options and have the bonding experience be more of a back-and-forth conversation to share memories with your grandfather. Just a thought!