Not bad! I like the way you've reversed the role of the game, but still have it with that sense of Flappy Bird. I was never very good at the original, and I'm not good at this. Think my highest score was 4! The hitbox seems to be a square around the fish's most extreme pixels, so it feel quite unforgiving. In Mark Brown's tutorial he shows how you can make the colliders just smaller than the sprite to help with this unfairness. I suppose the original Flappy Bird was also unforgiving in the same kind of way though.
Wish it had a high-score counter somewhere. When you die, you just have to remember your best ever score. Could save that to PlayerPrefs for extra credit...
Well done for finishing and submitting. Not an easy feat at all!