I've made some additional progress here, which is good, but it's led to some further questions. First, I don't need underwater cameras, so I switched from the double-sided to single-sided shader. That isn't a total fix, but it did help. Second, I've ruled out the water plane mesh as a source of the problem. I checked its poly count and found that it's quite reasonable. Also, replacing it with a Unity-provided Plane doesn't change anything. Third, the AquasReflection component seems to be the area of concern. What I observe is that I can change the overall poly count enormously by turning that component on and off, and it's related to how many objects are in the layer(s) being reflected according to this component's culling mask. I started with about 30 million polys in the scene, with a newly-created water material using the 1-sided shader. When I added my default layer to the culling mask for AquasReflection, the scene poly count jumps by about the same as the total polys in the default layer (about 20 million) per water plane. Disable the AquasReflection component, and the poly count goes down. Interestingly, removing the default layer from the culling mask with the component still enabled has no poly count effect. I suspect what's going on is that I'm somehow having this component try to reflect every poly in the applicable layers of the scene. I see an option to "ignore occlusion culling", but i have that disabled. Just about every object in the scene is occlusion static, and I have rebaked the occlusion quite often. Any idea what I'm doing wrong here?