Thank you very much for playing the game, i really appreciate it! There is no way to replenish health. That said, there are other survivors on the planet that can help you… (hint, one survivor is in the first level, not far from where you start, and they boost your oxygen. Theres another early in level two that sigificantly boosts your attack and defense). Good luck if you try the game again. If not, i still thank you very much for playing.
PS. The “fish” is supposed to be a broken off fan blade. Didn’t have the time to explain it, so, fair enough observation from your point of view.