Thanks for the fast responses. I've attached 3 photos that should help; hopefully, I shrunk them down to 800 pixels and they load correctly:
Pic1 is a photo taken from a couple of feet away. This one actually shows the water flowing out of that "side pipe."
Pic2 is a closer photo will a better view of the tub pipes. The PVC pipe that goes to the right is the one connected to the tub drain. That metal pipe that goes to the left is the one where the water is flowing out.
Pic3 is just a closer, hopefully better, view of the pipes coming down from the tub.
The drainage pipes are old (originals from when the house was built), but all the cold/hot water pipes (the red ones) were just installed a couple of years ago. I have a well/septic tank if that matters at all. I don't see any leaking, no matter how small, from any other drainage pipes, and these pipes aren't "leaking" as such; the only problem I can see is what Pic1 is showing, which is the water gushing out of that side left pipe.
Once again, thanks for the help.