The water plugin will eventually include many types of water depending on what you need to do with it. For instance there could be a physics simulated ocean and just a cheaper ocean that's mainly just for show. I ran into an article last week on screenspace ocean. It's a post process effect instead of a giant mesh. I figured it would be fun to try so I gave it a go. It's not finished but it shows the basic premise pretty well:
One thing I like about the screenspace technique is that you don't need high a polygon count to get smooth waves. I should mention the waves are just a heightmap, I didn't put in any wave generation algorithms yet.