Tidal motion happens twice a day. The back-and-forth motion of the waves can power turbines at all points along the shoreline. Tidal energy may not completely replace nuclear power, but coastal areas can benefit from the motion of the waves much like hydroelectric power at dams. With tidal energy, there won't be a need for dams, just for turbines underneath the surface of the water.
Over the next couple of centuries humans are going to have to find more efficient and cost effective electrical sources. I do not believe tidal energy should be substituted for nuclear energy because we most likely need both sources in the future. Tidal energy poses some hopeful options, but since it is newer, we are not fully aware of all of its downfalls.