My Simms Freestone generic “goretex type” chest waders weigh in at 800g, which would be a lot lighter than neoprenes (and I accept that they wouldn’t insulate or float as well, but in Oz and NZ this isn’t such an issue - wrong…the floating is, but not the insulation bit). I normally use a 1/2mm neoprene top for the top half of me, which presumably equates to a “semi-dry” top, as it hinders water entry to the bottom bits, and stops “ballooning” - obviously this could be thicker in colder weather, although looking at some of the photos of rafting with ice on the river rocks, I think I’d be lashing out for a full Kokotat dry suit for these trips!