Answer:
Advantages
No air pollution.
Once you've built the technology, it's free.
It needs no fuel and is totally renewable.
Tides are totally predictable and reliable.
Offshore turbines have low environmental impact.
Disadvantages
.
Barrages are expensive to build.
Barrages have high environmental impact,
much like hydroelectric dams.
It only provides power about 10 hours each day,
when the tide is moving in or out.
It is limited to coastal areas.
It must be able to withstand storms.
For more information go to http://home.clara.net/darvill/altenerg/tidalquiz.htm