I agree with SpiritCrusher the lakes sections in SAZ are a little boring, after you fall in the water you have to find a spring and return to the outside. Those sections don't offer any challenge and are boring, luckly the rest of the level are really well done. I suggest you to use the jet jaw in water areas, i know that you don't want to use the same enemie for different zones, but sometimes i think that some enemies could be placed again in another zone to make it more interesting (in SAZ and SNZ jet jaw in water areas, in SWZ crawla commander, popup turret, snailers or jetty-syns for outsides areas), also i think you could remove some enemies in AAZ and replace by others (green turtle, snailer, pointys, BUSH).