This is a really great idea.
It is one if not the best idea :D

Good Job!

This is a real grower of a game. I got more into it the more I played. The thing I really love about this is the surpising amount of depth that comes out of essentially having two scoring systems in one endless runner - the first being the distance you've travelled (your score), and the second being your tsunami level (your health, essentially). The more your tsunami level, the more you can survive hitting the rocks, but it also makes you larger, which means you're more likely to hit rocks but also more likely to pick up surfers and make your wave even bigger. The trade-offs are impressively nuanced for such a simple concept! 

In terms of critiques, I think my main thing is that it's just a bit too hard as it currently stands. I agree with the previous commenter about the wave movement being too abrupt. Also, you've given the wave a smaller hit box than its sprite, which is a good idea as it makes it easier to dodge rocks, but it also makes it harder to collect surfers. I think having two separate hit-boxes (one small one for rocks, and one large one for surfers) would make the game feel a good bit smoother. 

Other than that I think this is a very impressive first game, and you should be incredibly proud of yourself. Well done dev! 

Overrall i love the gameplay. The music is kind of synchronised with the surfers movement, and the sfx are good. The only issue i had was about the control of the wave, it is kind of abrupt, it is not smooth and that makes it difficult to correctly dodge through rocks. As you said this is your first game, i understand.

Good luck!