It's treated, but they don't last.. Even the fixed blades salt and h1 series will rust.. they are resistant/stainless, but not rust proof.. Unless the user is one to always dismantle the blade and do an all round maintenance on the pivots and internals, it's better to just use a fixed blade..
Post dive already there is alot of equipment to wash and clean, I'm the lazy kind and just soak my shears and blade in fresh water and glob a generous amount of petroleum jelly pre and post dive..
EDIT: By the way, rust or not, the knife is still functional.. I carry a stainless mora that has rust but I still use them and they function still.. so as long as u dun mind rust, it's fine.. I'm just referring to the concern on the effects of rust and weakening of the structural pivot which might affect safety in a dive that's all.
Always have a backup.