Forget all the bling you might see on the frames, its ALL about the lenses. The Wave 400's are what most folks buy lens wise. For general use and offshore the grey lens is better than the amber. The blue mirror is a grey lens while the green mirror is an amber lens. For inshore and low light conditions the amber lens is better. The grey just mutes the brightness of the lens without distorting the real color. The mirror helps reflect the light that is reflecting off of the water. The amber and vermillion lens helps increase contrast and is better suited for inshore sight casting and low light conditions. It tends to be a bit brighter than the grey. If you can afford it, get a pair with the Wave 580 lenses. The clarity of the lens will amaze you. Of course if you are stepping up from gas station throw downs to Costa's you will be amazed no matte what Costa model you get.
Costa service is pretty good, albeit a bit slow. Basically, if you break them you pay cost for a new pair which is about 50% off. If its a manufacturing problem they give you a new pair.
Regarding polarization and depth you can see well that's more an issue of water clarity than anything else. Yes polarized lenses will filter the light rays that are not hitting the lens straight on so you can usually see down through the surface of the water. To see any deeper is just water clarity. There are times that you will take them off and see better though. All in all it's worth it.
I'm no Costa dealer I've just been wearing them for a long time and I have crummy eyesight so I need all the help I can get.
Really though, any brand of high quality sunglasses are going to perform about the same whether you get Costa's, Kaenon, Smith, Oakley deep blue etc.
