Any suggestions on how the PCs are suppose to navigate this area?
My players never wanted anything to do with the Azoth caverns. They saw lakes full of highly flammable poison and just shut the doors. I suppose players could purchase a small boat or build a raft to travel through the caverns, or use a Fly spell. They can also use the levers controlling the depths of the azoth lakes to expose some areas. Pray they don’t drop a torch onto the azoth.
This is part of the fun of an old school module. They'll try stuff amd you'll figure it out.
My players never risked floating on the lakes of azoth. They DID find the azoth processor and the environment suits. They set up an azoth refining operation instead.