Except pants with sock can potentially fill up and drown you. bibs are much safer. Avoive pants with socks at all costs
I think all that have been suggested have been bibs. I've see the socks being more dangerous than gasketed pants a lot, and it has never made sense. I have a pair of drypants with gaskets- I assure you that any water in the pants is not leaving. I'm assuming the argument is that you could stick a finger in the gasket, and pull it open to drain? Would only drain what water is above the water line- for example, pants are full of water- if person is floating down the river, pants full of water, and reaches down and is able to pull gasket open, nothing will happen. If they can get to shore, and stand in knee deep water- then pull gasket open, water will drain to knee. This is all assuming you can get a finger in the gasket, which I'm pretty sure I couldn't do in an on river situation.
Drypants, whether with socks or gaskets, share the same risk. Which if mated with a top, is pretty minimal. Of course a bib is even less likely to fill with water, but I dont think theres a drypant out there doesn't have a neoprene waist or something that will minimize water entry- not neccesarily dry, but even without a top, they aren't really going to fill up- water pressure presses them against the legs, and there is no longer a big space to fill with water.