Kepler did not discover anything about the tides. He was primarily known for his work on planetary motion and astronomy, specifically the laws of planetary motion that bear his name.

The understanding of tides is primarily attributed to Isaac Newton and his theory of universal gravitation. Newton explained that the gravitational pull of the Moon and the Sun on the Earth's oceans causes the bulges of water we experience as high tides.

While Kepler's work was fundamental to our understanding of the solar system, it did not directly contribute to the explanation of tides.