Tidal currents are the horizontal movements of water caused by the gravitational interaction between the Earth, Moon, and Sun. These currents are influenced by various factors such as the shape of coastlines, coastal features like islands, bays, and estuaries, and the combined effect of tides and ocean currents. Among the given options, option 'A' best describes tidal currents.

Tidal currents occur in areas where tides are channeled between islands, bays, and estuaries. This happens because these coastal features act as barriers or funnels, causing the water to flow in a particular direction as the tides rise and fall. As the tide rises, water flows into these confined areas, creating a tidal current that can be quite strong. Similarly, as the tide falls, water flows out of these areas, generating another tidal current in the opposite direction. This alternating flow of water creates tidal currents that are characteristic of these regions.

The interaction between tides and ocean currents can also lead to the formation of tidal currents. Option 'B' describes this phenomenon. When tides and ocean currents move in the same direction, they combine to create stronger currents. This occurs in areas where the tidal motion aligns with the direction of the prevailing ocean currents, amplifying the flow of water.

Deep water ocean currents associated with neap tides are described in option 'C'. Neap tides occur when the gravitational forces of the Moon and Sun are perpendicular to each other, resulting in lower tidal range. During neap tides, deep water ocean currents may be influenced by other factors such as wind patterns, temperature gradients, and the shape of ocean basins.

Option 'D' refers to strong tides that have a high potential to extract tidal energy. Tidal energy is a form of renewable energy that can be harnessed from the movement of water during tides. Strong tides, characterized by a large tidal range, provide greater kinetic energy that can be converted into electricity. However, this option is not an accurate description of tidal currents.

In conclusion, option 'A' is the correct answer as it accurately describes tidal currents as tides that are channeled between islands, bays, and estuaries.