Sun is undoubtedly the most plentiful energy source we have, BUT... There is a disadvantage - the huge area of land that needs to be covered by solar panels in a power plant. Panels are way more helpful on rooftops than on land that could be used for farming or habitation. And sun isn't available all 24 hours.

Ocean wave and current energy, is a result of wind, which further is caused by temperature difference in the atmosphere... caused by our sun. So ocean energy is essentially indirect solar energy, and we don't require any land in this case. Population is rising, there will be more mouths that need feeding and we will need more shelters as well. Plus wind blows almost all day and night, so waves and currents are available almost all day and night.

Thanks for asking.