At 5 meters of depth, the human eye ceases to perceive red color, at ten - orange. For twenty people no longer sees yellow, for thirty - green. And at 60 meters, the blue color disappears, and you fall into pitch darkness. This series of books is about those who dive deeper! The story of a former combat swimmer who fell into the body of a teenager from a tribe, where the ability to dive deep is an exceptional ability of a small caste. After all, diving even ten meters for an ordinary farmer is something prohibitive. And only people of the "deep caste" are immersed in twenty or a little more. But... is twenty meters deep?