The correct answer is option 3: Tides. Tides are the periodic rise and fall of ocean water that occur due to the gravitational forces exerted by the Moon and the Sun on Earth. The gravitational pull of the Moon is stronger than that of the Sun, resulting in two high tides and two low tides approximately every 24 hours and 50 minutes. Tides can also be influenced by the shape and depth of the ocean basins, as well as the alignment of the Sun, Moon, and Earth.

Option 1: Current refers to the continuous flow of water in a particular direction, such as ocean currents or river currents. While tides can affect currents, they are not synonymous.

Option 2: Waves are the movement of water on the surface of the ocean, usually caused by wind. Waves can be influenced by tides, but they are not the same phenomenon.

Option 4: Tsunamis are large ocean waves caused by earthquakes, volcanic eruptions, or underwater landslides. Tsunamis are unrelated to the regular rise and fall of tides.

In summary, tides refer to the periodic rise and fall of ocean water due to gravitational forces, caused primarily by the Moon and the Sun.