Can someone tell me how to create rotor wash from a helicopter when it hovers over water?

I'd animate a texture map. Shoe String Graphics (http://www.des-web.net/html/shoestring_shaders.html) has a shader called Proximity which would make this much easier. They haven't released an update for C6 yet however. If you're still using C5, then it won't be an isue though. Another option is to create a movie effect with any of the vide special effects softtwares out there and import as a texture onto a vertex object that is just slightly above the other water in your scene.

Following on from Marks idea maybe. A disk, just above the water and the same water colour. apply some roughness to it and apply a circular gradation. Then apply circular motion.

Does this make sense? (I have set myself a task for today---though I do have that plugin as well!)

The principle seems pretty simple. I used a Vertex Circle. Applied a different (Rough Sea) texture Added that rough sea texture into the displacement tab and adjusted displacement. Added Spin (Modifier Tab) Getting that circle to track in relation to the helecopter movement should not be difficult.

BUT, I can not seem to be able to work out, in Carrara, to do a  circular gradient where the edges would gradually soften off to clear.  Maybe Mark can help?

Thanks, I will give it a try..
I have both Carrara 5 and 6 Pro..

I just did another movie with the circle exactly at the plane Z level, and I added 12% Gausian Blur (Effects Tab). I think that improved even better! 

Hey,
Thanks a lot keep'em coming

Here's an option.  I created an animation of concentric rings radiating out from a central source.  (I used the "radio waves" filter in AfterEffects, but you could do the same in any number of programs.)  I put this into the bump channel of the shader for this plane along with a fractal noise generator (in add mode).  I spent about 5 minutes throwing this together; if you spent more time animating the concentric rings and also animating the texture of the water (this is just a color and bump), it could look pretty good.

HTH.

 - Dex

Hmm.  Used to be I could post animated gifs with responses.  But it's not showing up....

Ah, is there a gallery or somewhere that I can post the 4 second animated gif?  it's 730 K, and apparently too big to post in the forum....

You might be able to upload it to YouTube, or to http://www.sharecg.com. The advantage of posting it on the latter is not only is it free, but you can actually get paid for the amount of hits your upload receives, whether it's a texture, shader, model, tutorial, animation, etc.