Given a scientific passage and an answer, generate a question for the given answer.

Passage: If you've ever visited an ocean shore, then you know that ocean water is always moving. Waves ripple through the water, as shown in Figure below . The water slowly rises and falls because of tides. You may see signs warning of currents that flow close to shore. What causes all these ocean motions? Different types of motions have different causes. Answer: tides
What is the term for when the water of the ocean slowly rises and falls?