Very true, my set right now are hard sole..love them in the local waters but at the ocean, those little channels in the soles fill with sand and get lumpy just like you said, then you have to rip the liner and wash them after ever hunt..a real pain..If you go with dive boots, I'd advise against the hard-soled ones...that honeycomb structure eventually and permanently fills with fine sand and causes lumps. The thinner, more flexible soles do surprisingly well.