Lumen doesn't like large areas of realtime water

I'm working on a reasonably large/detailed realtime scene of a Marina....I'm testing Lumen and the scene has a good frame rate around 30 - 40 fps. The problem I have is that the water material always looks low res and ruins the scene as it's obviously a main feature. The water looks great in standard mode...it's a shame TM can't do material overrides and just set the water to standard mode. Are there any other tips someone may have to help with this?...Thanks