I'm sure this applies to you 2ns gens but on my rear diff theres a breather. Little cap looking thing. It expands when the diff gets hot so it can 'breathe'. The downfall to that is if you buried your rear axle in water, well its going to suck in water and ruin your diff internals (if you dont drain and change fluids right away)
So what you can do is go to Toyota and order a union (like $3) and it screws into where the original breather head is. Then with a couple hose clamps, put a new hose on there and redirect it to somewhere where it won't suck up water.
Mine is in the engine bay up against the firewall (cause if that's in water, I have worse problems to deal with) Some guys will run it to next to their fuel filler neck so its in that door. I put a spectre filter on the end so it won't suck in dust or any of the sort.