Tidal and current energy is less susceptible to climate change and can produce energy both day and night.
Tidal currents result from the rise and fall of the tide and are intensified by confinement or seabed bathymetry. They are highly predictable in terms of timing & magnitude. Likewise, ocean currents exist in open oceans and flow regularly in the same direction with low variability. They are due to regional differences in temperature and salinity across the globe and the Coriolis effect due to the rotation of the Earth.