The idea is great, needs to be evolved. I don't get why the player shouldn't just click a breath button when the progress bar is on 2/3. So, I guess you need to add something, that motivates the player to get a risk to be eaten by a shark. For example, add stamina and make stamina-bonuses visible only when player oxygen is under 50% or something like this. And yep, we need more variations of levels! :)