Underside of a travel trailer - swelling?

[WItoTX]

just pushing on it with your hands should tell you water or not, I would think you could feel it

OP, do this. It doesn't look right to me.

[KY2TX]

Could also be tank swell or tank mounts broken/ loose

[Philip-TX]

Could also be tank swell or tank mounts broken/ loose

x2^^

Be careful if you follow the poke a hole in it advice. The is a tank up the somewhere you don't want to poke a hole in.

Just pull the coreplast down a see what's going on.

[dallred]

I had the same problem and it was caused by rodents nesting in it. Hard to stop them once they claim a spot.