Water leak

[Brizo]

I bought a Clayton homes mobile home and noticed I had a leak under the house. I cut a hole in the insulation and water just poured out. When I looked in the hole however, I don't see any water pipes. All I see is a square metal duct. I'm assuming the plumbing is running inside this? How do get to the pipe in order to fix it? Need some advice om not an idiot but I don't want to damage anything while trying to fix it.