I'm getting tired, but yeah, some people have been working on this.  I'm not sure what the status is on the research.

The problem is the buoyancy greatly minimizes the force of the mass. The second problem is the angle differential between the mass vector and the generator input. You'd be better off with the generators horizontally at sea level, directly in line with the mass vector.

Your whole design would be better if you had a very large, 'barn door' on hinges submerged, with the cables attached midway up the free swinging end, transferring the motion of the currents into the generators submerged horizontally to the midway attachment point. The mass of the ocean would be a more efficient transfer of polar moment of inertia with the barn door type lever, than a floating 'rubber duck' type mass.

In any event, it's not nearly as efficient, or cost effective as using gravity to pull water down past an impeller, or wind past an impeller, or converting solar energy using screen printed solar panels, in terms of 'free energy'.

Well, a friend's son is working on a degree in mechanical engineering and this is one of his projects. I am not really clear on the details of what he is doing (but then at his level, he probably in not all that clear either).

His system involves a long string of floats where the flex of the joints provides the motion for the system. I don't know what he is using for transducers. Even so, it seems to me that there are a couple of things to take into account.

First, the mechanical resistance in the joints has to be lower than the energy available in a single wave or the system would not flex much, if at all.

Second, the length of each floating element would have to be close to or just below the nominal wavelength for any given location in order to get the best use of the waves. That is likely to be somewhat specific to a given location.

Then too, if deep water is available, any storms could temporarily change the dominant wavelength, thus rendering the system less effective until the seas calm down again.

You would probably double the potential power output just by simply adding a keel to the bottom of the float, but it would still be grossly inefficient compared to existing free energy systems.

 You couldn't get a more stable (24/7) output than a hydroelectric dam, and the higher the dam, the more energy the water has due to gravitational force.
 
Due to gravity, it takes just under 28 square inches of water (at rest) to equal 1 PSI of downward force.
Factor in the leverage ratio of your impeller geometry, it's reciprocating mass, and efficiency of your generator, and you can calculate the amount of watts you can generate from the mass of the water acting upon the lever.
 
The beauty of windmills is their low initial cost, and the maintenance costs vs power output. Same with screen printed solar cells. If you could automate and scale up production, the unit costs of both of these systems would drop exponentially.
 
As far as your design, the 2 major flaws are the angle differential between the force acting upon your float, and the generator. A very simply way to model it in your mind, is to think of it in reverse.
Imagine if you were in a boat trying to pull your barge (float) along the water. Would you attach the line to the transom, in line with the barge, or would you tie the line to the top of a 40' mast?
The second thing you have to take into account is how little force it takes to move a large mass floating on water, due to the low coefficient of drag between the vessel and the fluid. This is why large ocean liners can by 'tugged' by little boats, with a few hundred horsepower with props that are only a handful of inches in diameter.
 

Nearly a concept wind waves grow if you talk something up and down. The only problem is to design something that will not require maintenance every two days and profitability.

That's true it can.  It's also possible to use other forms of energy storage for the same thing, but pump storage combined with existing hydro plants is probably the most cost effective methods.  

I've been doing a lot of reading about renewable energy lately.  It seems that if we are going to have any kind of bright future renewable energy is needed.   Based on what I read there seems to be four different ways to integrate variable energy sources into the grid. 

Demand side management:  This includes things like smart girds, price incentives and any other ways to directly or indirectly control how customers use power.  

Supply side management:  This included all kinds of dispatchable generation.   Some examples of which include hydro plants, gas turbines, and spinning reserve.  

Improved grids and electricity markets:  This includes things like uniform grid protocols, energy trading between countries, and supper grids.  The idea behind these being that if you can connect a lot of variable sources with a lot of variable demand that it will average out somehow.  Actually I'm not to sure about the whole supper grid idea.  I was wondering if you could give me your opinion on it.  You know a lot more about electronics then I do. 

Energy storage:  This includes a number of different technologies.  I found a fairly good table on line. 

"The two main applications of energy storage technologies are for power – driven by the needs for power quality and bridging power – and for energy management. In power applications, stored energy is only applied for seconds or less to assure continuity of quality power, or it might be used for slightly longer (a few minutes) to assure continuity of service when switching from one source of energy generation to another. For energy management applications, storage media is used to decouple the timing of generation and consumption of electric energy, as previously described. A typical application is load leveling, which involves the charging of storage when energy cost is low and utilization as needed. "

http://energystoragetrends.blogspot.com/2010/11/energy-storage-basics.html

Over all I think integrating variable power is possible, but difficult.  Given thing like global warming and peek oil it is also probably necessary.