Thanks both the difficulty and the minigame both had some fixes released in the last few minutes. I did a playthrough and
More items and fish closer to surface, enemies deal less damage, little bit longer between waves, decreased enemy health.
I feel like I made it a good balance between hard and easy. where you have to keep improving.
I have some interesting ideas to create some caves, lighting under water, Treasure with upgrades. and some more underwater mechanics.