[Nwoko]

How do you fix a bath tub that leaks under the building?

How do you remove the pool of water under the building?

How do you threat the smell that comes from the water pool?

[speedball1]

How do you fix a bath tub that leaks under the building

I take it that you have a crawl space to work with. First you mist locate the source of the leak.(see image). Get back with what you find.

How do you remove the pool of water under the building

If it's a lot of water you can dig a trench and drain it away. If it's not so large you can spread dirt over it.

How do you threat the smell that comes from the water pool?

You spread quick lime over the area.
Good luck and thank you for rating my reply, Tom