Celica Forums General Discussion General Water in rear cavity passenger rear taillight

I have a pool of water.in my rear cavity near the passemger rear taillight how do i drain it out? Car is a celica gt 2000 no sunroof bought the car 2 years ago there was never a sign of a leak o just found it because i had snails in my taillight also found cardboard and what it looks like a sponge inside the cavity pic below i just want to drain it out so it does not rust can anyone help me?

I have the same issue but havent solved where its coming from. But i use a wet vac with a long flexible hose to suck up the water.