This renewable source works by using the waves to create energy.
Scientists have had trouble building a machine that can withstand the constant corrosive effects of the salt water. Currently, tidal and wave power is worldwide and has 81 ocean energy programs in progress. The energy comes from the salinity, thermal gradients, currents and waves. Of course, the machinery is quite complicated and advanced which is why there are different parts for different types of waves and tides. So far, the parts are:

~Nodding Duck :

The duck rotates with a nodding motion as the strength of the waves pass. The motion drives the hydraulic arm, which then generates power.

The rolling wave movement causes the hinged sections to rise and fall; this motion drives the hydraulic arm and produces the power.
The bobbing up down motion from passing waves drives the piston inside a tube, which is attached to the sea floor.
~Submerged Buoys:
High pressure is pumped by the wave motion that drives the piston up and down. The seawater ashore drives the turbine to generate power for the grid or to desalinate the seawater.


Benefits and Positives:
Lucky for us, Australia, Western Europe and America have the best wave energy available to us. Scientists and engineers are working on wave power projects and have great hopes for the rapid reduction in the cost as technology develops. For example, wind power was once decided as too expensive but costs have gone down by 80% since first developed.
Did you know?
The ocean energy is projected to supply 25 billion KWH of electricity by 2030, which is amazingly enough to power 2 cities the size of Melbourne for a year. The average city home’s daily electricity consumption is 20 KWH and the daily water usage is 350L. One unit is expected to be capable of producing enough power for 1500 homes and enough water for 9000 houses.
Tidal Power --everything done by the tides

How it works:
Each time the water flows in or out, it turns a turbine inside a power generator which produces electricity. The tidal power generator is a type of bridge that blocks the mouth of an estuary so that the tide has to move through it. The positives and benefits are very much like wave power, and as mentioned before, is still in progress to improve the devices and technology.