So I played it for a while and I kinda ended up trying to reach the seafloor as much as possible, as that would give me more points on the way up. That meant I aimed more for not hitting the fish on the way down, and then letting the hook get things on the way up. I'm not sure if this is the intended way to play, but I had a bit of fun with it. 

Yea, so a really good thing you can do is too look for those things in your prototype that is fun, and then enhance them and give them space. For me the fun thing was to try and reach the bottom, so I'd double down on that. When you think you have figured out what the fun way to play is, make it even more fun, and make it interesting! What you could do here is a lot of things really, but the main things that pop up into my head are:

• Being able to control the hook a bit on its way up and down
• Making it clearer that you get higher score for fish deeper down
• Give a bonus for getting to the seafloor

Basically, you can reward the player when they play in a fun and interesting way to make them play more in that way.

It's nice to see that you tried to polish it up a bit as well, well done!

Great work!