Final answer:
Tides are the alternating rising and falling of sea levels caused by the Moon's gravitational pull. The recorded values show the tide rise over a 15-day period.
Step-by-step explanation:
Tides are the alternating rising and falling of sea levels caused by the difference in the strength of the Moon's gravitational pull on different parts of Earth. The height of tides can vary depending on various factors such as the local shoreline topography and ocean floor depth. In the given data of a surfer recording the tide rise over a 15-day period, the values are: 2, 5, 7, 8, 9, 10, 13, 14, 18, 19, 20, 20, 21, 22, and 24 feet.