| A | B |
|---|
| continental shelf | the shallow part of the ocean at the edge of the continents |
| continental slope | the edge of the continental shelf that extends steeply downward to the ocean floor |
| ocean basin | the floor of the deep ocean |
| trench | a deep, narrow valley in the ocean floor |
| ridge | the highest part of a chain of underwater mountains |
| current | a riverlike flow of water in the ocean |
| tide | the rise and fall of the surface level of the ocean |
| wave | the up-and-down movement of ocean water caused by the wind |
| light zone | the sunlit waters of the ocean |
| dark zone | the ocean water where sunlight does not reach |
| coral reef | a platform or ridge of coral at or near the ocean surface |
