Pull the switch.
Also I can't find any abandoned mineshaft chests despite already finding 3 or 4 abandoned mineshafts :(
Also I think Ender Pearls should be useable as an antidote (smelt them into an 'Antidote' which can be crafted with a bucket to make an 'Antidote Bucket', or just do step 2 with no smelting or something like that) since Endermen are quite common (I've found at least one one pretty much every single night I've been playing except for when I was sailing, but stil lsaw some from a distance).