[Micah]

Empowering a shaman to clam once you hit construction 6 is only 85W, plus another 35 for a Naiad after that (for 2/turn), or 10 clams worth of water gems. After that everyone's able to forge them. While a 10 pearl/turn advantage is really nice it's hardly game-breaking. That's also a worst-case scenario as far as finding indy mages or access to Naiads goes, especially since enchantresses are fairly common. The clamming nations also get a slight bump in early-game production, but non-clam nations can make that up by casting a gem global with their stocked gems once the research is available to do so. Again, an advantage for the clammers, but not one that's broken compared to other game options, especially considering how lousy water magic is. If your nationals have W they're giving up some other path that's more useful in other areas.