water filled metal trough

I have a client who just bought a house in a small rural community on MD's Eastern Shore. A section of the hardwood living room floor, directly in the center of the house, had boards that had obviously once been cut to permit access to the dirt crawlspace below (we think)

She removed the boards so that mold removal experts could get in and discovered some kind of a metal"trough" filled with stagnant, but transparent water directly under the area where she removed the boards.

The trough is about 4 x 2 ft. wide and seems to be about 2 ft. deep. No odor emits from the water. Have you ever seen anything like this before? Do you know what it is or was, and how do you think that water gets into it and what, if anything, should she do about it?

Thanks in advance for any thoughts on this

pit

Apparently it has no drain connections or any other openings from your description. Without being there to evaluate it we cannot answer your questions. It might have something to do with an old floor furnace.

There must be water entering from somewhere or it would have evapourated after a few years. Is it possibly a rain water storage cistern? Some friends in rural Quebec have a storage cistern that, once upon a time, was connected to a pump in the kitchen sink. I believe now it just sits empty. It was originally connected to collect rain water and shunt the overflow into a dry well outside somewhere.

I think the size would say it's not a cistern.